Chapter 1

The Study of Life

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Summary

The main goal of basic science is to expand knowledge without any expectation of short-term practical application of that knowledge. Biology is the science that studies living organisms and their interactions with one another and their environments. Those fields related to the physical world and its phenomena are natural sciences Inductive reasoning uses particular results to produce general scientific principles.

Key terms

natural science

field of science that is related to the physical world and its phenomena and processes

results

section of a scientific paper in which the author narrates the experimental findings and presents relevant figures, pictures, diagrams, graphs, and tables, without any further…

science

knowledge that covers general truths or the operation of general laws, especially when acquired and tested by the scientific method

basic science

science that seeks to expand knowledge and understanding regardless of the short-term application of that knowledge

deductive reasoning

form of logical thinking that uses a general inclusive statement to predict specific results

inductive reasoning

form of logical thinking that uses related observations to arrive at a general conclusion

organ

collection of related tissues grouped together performing a common function

Chapter 2

The Chemical Foundation of Life

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Summary

Atoms, which consist of protons, neutrons, and electrons, are the smallest units of an element that retain all of the properties of that element. Electrons can transfer, share, or cause charge disparities between atoms to create bonds, including ionic, covalent, and hydrogen bonds, as well as van der Waals interactions Hydrogen bonds allow ions and other polar molecules to dissolve in water. All of the 98 elements that occur naturally have unique qualities that allow them to combine in various ways to create molecules, which in turn combine to form cells, tissues, organ systems, and organisms.

Key terms

ion

atom or chemical group that does not contain equal numbers of protons and electrons

van der Waals interaction

very weak interaction between molecules due to temporary charges attracting atoms that are very close together

electron

negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of -1 unit

element

one of 118 unique substances that cannot break down into smaller substances; each element has unique properties and a specified number of protons

hydrogen bond

weak bond between slightly positively charged hydrogen atoms and slightly negatively charged atoms in other molecules

proton

positively charged particle that resides in the atom's nucleus; has a mass of one amu and a charge of +1

atom

the smallest unit of matter that retains all of the chemical properties of an element

neutron

uncharged particle that resides in an atom's nucleus; has a mass of one amu

Chapter 3

Biological Macromolecules

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Summary

Proteins, carbohydrates, nucleic acids, and lipids are the four major classes of biological macromolecules—large molecules necessary for life that are built from smaller organic molecules. Macromolecules are comprised of single units scientists call monomers that are joined by covalent bonds to form larger polymers. When polymers break down into smaller units (monomers), they use a water molecule for each bond broken by these reactions. The polymer is more than the sum of its parts: it acquires new characteristics, and leads to an osmotic pressure that is much lower than that formed by its ingredients.

Key terms

biological macromolecule

large molecule necessary for life that is built from smaller organic molecules

carbohydrate

biological macromolecule in which the ratio of carbon to hydrogen and to oxygen is 1:2:1; carbohydrates serve as energy sources and structural support in cells and form…

polymer

chain of monomer residues that covalent bonds link; polymerization is the process of polymer formation from monomers by condensation

lipid

macromolecule that is nonpolar and insoluble in water

monomer

smallest unit of larger molecules that are polymers

nucleic acid

biological macromolecule that carries the cell's genetic blueprint and carries instructions for the cell's functioning

hydrolysis

reaction that causes breakdown of larger molecules into smaller molecules by utilizing water

protein

biological macromolecule comprised of one or more amino acid chains

Chapter 4

Cell Structure

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Summary

All prokaryotes have plasma membranes, cytoplasm, ribosomes, and DNA that is not membrane-bound. Electron microscopes provide higher magnification, higher resolution, and more detail than light microscopes. The unified cell theory states that one or more cells comprise all organisms, the cell is the basic unit of life, and new cells arise from existing cells Prokaryotes are single-celled organisms of the domains Bacteria and Archaea.

Key terms

cell

the smallest unit of life

unified cell theory

a biological concept that states that one or more cells comprise all organisms; the cell is the basic unit of life; and new cells arise from existing cells

cell wall

rigid cell covering comprised of various molecules that protects the cell, provides structural support, and gives shape to the cell

cytoplasm

entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals

electron microscope

an instrument that magnifies an object using an electron beam that passes and bends through a lens system to visualize a specimen

light microscope

an instrument that magnifies an object using a beam of visible light that passes and bends through a lens system to visualize a specimen

plasma membrane

phospholipid bilayer with embedded (integral) or attached (peripheral) proteins, and separates the cell's internal content from its surrounding environment

prokaryote

unicellular organism that lacks a nucleus or any other membrane-bound organelle

Chapter 5

Structure and Function of Plasma Membranes

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Summary

Modern scientists refer to the plasma membrane as the fluid mosaic model. A phospholipid bilayer comprises the plasma membrane, with hydrophobic, fatty acid tails in contact with each other. The membrane's landscape is studded with proteins, some which span the membrane. The membrane's fluid nature is due to temperature, fatty acid tail configuration (some kinked by double bonds), cholesterol presence embedded in the membrane, and the mosaic nature of the proteins and…

Key terms

fluid mosaic model

describes the plasma membrane's structure as a mosaic of components including phospholipids, cholesterol, proteins, glycoproteins, and glycolipids (sugar chains attached to…

membrane's fluid nature

due to temperature, fatty acid tail configuration (some kinked by double bonds), cholesterol presence embedded in the membrane, and the mosaic nature of the proteins and…

hydrophobic

molecule that does not have the ability to bond with water; “water-hating”

membrane's landscape

studded with proteins, some which span the membrane

plasmolysis

detaching the cell membrane from the cell wall and constricting the cell membrane when a plant cell is in a hypertonic solution

amphiphilic

molecule possessing a polar or charged area and a nonpolar or uncharged area capable of interacting with both hydrophilic and hydrophobic environments

clathrin

protein that coats the plasma membrane's inward-facing surface and assists in forming specialized structures, like coated pits, for phagocytosis

facilitated transport

process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins

Chapter 6

Metabolism

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Summary

Glucose synthesis and glucose breakdown are examples of anabolic and catabolic pathways, respectively A cell’s metabolism refers to the chemical reactions that take place within it. Objects in motion do physical work, and kinetic energy is the energy of objects in motion. Cells perform the functions of life through various chemical reactions.

Key terms

metabolism

all the chemical reactions that take place inside cells, including anabolism and catabolism

anabolic

(also, anabolism) pathways that require an energy input to synthesize complex molecules from simpler ones

catabolic

(also, catabolism) pathways in which complex molecules break down into simpler ones

kinetic energy

energy type that takes place with objects or particles in motion

coenzyme

small organic molecule, such as a vitamin or its derivative, which is required to enhance an enzyme's activity

heat

energy transferred from one system to another that is not work (energy of the molecules' motion or particles)

energy coupling

process during which energy released by one reaction is used to drive another reaction

free energy

Gibbs free energy is the usable energy, or energy that is available to do work

Chapter 7

Cellular Respiration

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Summary

The two processes of ATP regeneration that are used in conjunction with glucose catabolism are substrate-level phosphorylation and oxidative phosphorylation through the process of chemiosmosis When ATP is used in a reaction, the third phosphate is temporarily attached to a substrate in a process called phosphorylation. The structure of ATP is that of an RNA nucleotide with three phosphates attached. As ATP is used for energy, a phosphate group or two are detached, and either ADP or AMP is produced.

Key terms

chemiosmosis

process in which there is a production of adenosine triphosphate (ATP) in cellular metabolism by the involvement of a proton gradient across a membrane

phosphate group or two

detached, and either ADP or AMP is produced

substrate-level phosphorylation

production of ATP from ADP using the excess energy from a chemical reaction and a phosphate group from a reactant

phosphorylation

addition of a high-energy phosphate to a compound, usually a metabolic intermediate, a protein, or ADP

glycolysis

process of breaking glucose into two three-carbon molecules with the production of ATP and NADH

oxidative phosphorylation

production of ATP using the process of chemiosmosis in the presence of oxygen

third phosphate

temporarily attached to a substrate in a process called phosphorylation

structure of ATP

that of an RNA nucleotide with three phosphates attached

Chapter 8

Photosynthesis

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Summary

Only certain organisms (photoautotrophs), can perform photosynthesis; they require the presence of chlorophyll, a specialized pigment that absorbs certain wavelengths of the visible spectrum and can capture energy from… The pigments of the first part of photosynthesis, the light-dependent reactions, absorb energy from sunlight. The process of photosynthesis transformed life on Earth. Eukaryotic autotrophs, such as plants and algae, have organelles called chloroplasts in which photosynthesis takes place, and starch accumulates.

Key terms

light-dependent reaction

first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH)

pigment

molecule that is capable of absorbing certain wavelengths of light and reflecting others (which accounts for its color)

wavelength

distance between consecutive points of equal position (two crests or two troughs) of a wave in a graphic representation; inversely proportional to the energy of the radiation

process

less localized and occurs within folded membranes, extensions of the plasma membrane, and in the cytoplasm

photoautotroph

organism capable of producing its own organic compounds from sunlight

chloroplast

organelle in which photosynthesis takes place

light-independent reaction

second stage of photosynthesis, through which carbon dioxide is used to build carbohydrate molecules using energy from ATP and NADPH

photosystem

group of proteins, chlorophyll, and other pigments that are used in the light-dependent reactions of photosynthesis to absorb light energy and convert it into chemical energy

Chapter 9

Cell Communication

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Summary

Signaling cells secrete ligands that bind to target cells and initiate a chain of events within the target cell. The four categories of signaling in multicellular organisms are paracrine signaling, endocrine signaling, autocrine signaling, and direct signaling across gap junctions. Endocrine signals are carried long distances through the bloodstream by hormones, and autocrine signals are received by the same cell that sent the signal or other nearby cells of the same kind. Internal receptors are found in the cell cytoplasm.

Key terms

endocrine signal

long-distance signal that is delivered by ligands (hormones) traveling through an organism's circulatory system from the signaling cell to the target cell

internal receptor

(also, intracellular receptor) receptor protein that is located in the cytosol of a cell and binds to ligands that pass through the plasma membrane

paracrine signal

signal between nearby cells that is delivered by ligands traveling in the liquid medium in the space between the cells

autocrine signal

signal that is sent and received by the same or similar nearby cells

ligand

molecule produced by a signaling cell that binds with a specific receptor, delivering a signal in the process

signaling cell

cell that releases signal molecules that allow communication with another cell

target cell

cell that has a receptor for a signal or ligand from a signaling cell

receptor

protein in or on a target cell that bind to ligands

Chapter 10

Cell Reproduction

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Summary

Human gametes have 23 chromosomes, or one complete set of chromosomes; a set of chromosomes is complete with either one of the sex chromosomes, X or Y. An organism’s traits are determined by the genes inherited from each parent. Prokaryotes have a single circular chromosome composed of double-stranded DNA, whereas eukaryotes have multiple, linear chromosomes composed of chromatin wrapped around histones, all of which are surrounded by a… Genes are segments of DNA that code for a specific functional molecule (a protein or RNA).

Key terms

histone

one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes

chromatid

single DNA molecule of two strands of duplicated DNA and associated proteins held together at the centromere

cell cycle

ordered series of events involving cell growth and cell division that produces two new daughter cells

gene

physical and functional unit of heredity, a sequence of DNA that codes for a protein

gamete

haploid reproductive cell or sex cell (sperm, pollen grain, or egg)

set of chromosomes

complete with either one of the sex chromosomes, X or Y

organism’s traits

determined by the genes inherited from each parent

cyclin-dependent kinase (Cdk)

one of a group of protein kinases that helps to regulate the cell cycle when bound to cyclin; it functions to phosphorylate other proteins that are either activated or…

Chapter 11

Meiosis and Sexual Reproduction

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Summary

In most organisms, fertilization occurs between two haploid cells, the larger being called “female” or “egg” and the smaller being called “male” or “sperm." In most animals, meiosis is used to produce haploid eggs and… Meiosis generates variation in the daughter nuclei during crossover in prophase I as well as during the random alignment of tetrads at metaphase I. Sexual reproduction requires that organisms produce cells that can fuse during fertilization to produce offspring. The cells that are produced by meiosis are genetically unique

Key terms

meiosis

a nuclear division process that results in four haploid cells

meiosis I

first round of meiotic cell division; referred to as reduction division because the ploidy level is reduced from diploid to haploid

crossover

exchange of genetic material between nonsister chromatids resulting in chromosomes that incorporate genes from both parents of the organism

tetrad

two duplicated homologous chromosomes (four chromatids) bound together by chiasmata during prophase I

fertilization

union of two haploid cells from two individual organisms

meiosis II

second round of meiotic cell division following meiosis I; sister chromatids are separated into individual chromosomes, and the result is four unique haploid cells

reduction division

nuclear division that produces daughter nuclei each having one-half as many chromosome sets as the parental nucleus; meiosis I is a reduction division

Chapter 12

Mendel's Experiments and Heredity

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Summary

When the offspring in Mendel’s experiment were self-crossed, the F 2 offspring exhibited the dominant trait or the recessive trait in a 3:1 ratio, confirming that the recessive trait had been transmitted faithfully… Observable traits are referred to as dominant, and non-expressed traits are described as recessive. Reciprocal crosses generated identical F 1 and F 2 offspring ratios. Working with garden pea plants, Mendel found that crosses between parents that differed by one trait produced F 1 offspring that all expressed the traits of one parent.

Key terms

recessive

trait that appears “latent” or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive…

F 2

second filial generation produced when F 1 individuals are self-crossed or fertilized with each other

dominant

trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait

product rule

probability of two independent events occurring simultaneously can be calculated by multiplying the individual probabilities of each event occurring alone

reciprocal cross

paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross

F 1

first filial generation in a cross; the offspring of the parental generation

trait

variation in the physical appearance of a heritable characteristic

blending theory of inheritance

hypothetical inheritance pattern in which parental traits are blended together in the offspring to produce an intermediate physical appearance

Chapter 13

Modern Understandings of Inheritance

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Summary

Disorders in chromosome number, or aneuploidies, are typically lethal to the embryo, although a few trisomic genotypes are viable. Sutton and Boveri's Chromosomal Theory of Inheritance states that chromosomes are the vehicles of genetic heredity. Sturtevant devised a method to assess recombination frequency and infer linked genes' relative positions and distances on a chromosome on the basis of the average number of crossovers in the intervening region between… Whereas linkage causes alleles on the same chromosome to be inherited together, homologous recombination biases alleles toward an independent inheritance pattern

Key terms

Chromosomal Theory of Inheritance

theory proposing that chromosomes are the genes' vehicles and that their behavior during meiosis is the physical basis of the inheritance patterns that Mendel observed

recombination frequency

average number of crossovers between two alleles; observed as the number of nonparental types in a progeny's population

homologous recombination

process by which homologous chromosomes undergo reciprocal physical exchanges at their arms, also crossing over

aneuploid

individual with an error in chromosome number; includes chromosome segment deletions and duplications

euploid

individual with the appropriate number of chromosomes for their species

karyogram

a karyotype's photographic image

monosomy

otherwise diploid genotype in which one chromosome is missing

nondisjunction

failure of synapsed homologs to completely separate and migrate to separate poles during the meiosis' first cell division

Chapter 14

DNA Structure and Function

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Summary

Avery, MacLeod, and McCarty showed that DNA is required for the transformation of bacteria. Some of the salient features are that the two strands that make up the double helix have complementary base sequences and anti-parallel orientations. Alternating deoxyribose sugars and phosphates form the backbone of the structure, and the nitrogenous bases are stacked like rungs inside. DNA was first isolated from white blood cells by Friedrich Miescher, who called it nuclein because it was isolated from nuclei.

Key terms

transformation

process in which external DNA is taken up by a cell

salient features

that the two strands that make up the double helix have complementary base sequences and anti-parallel orientations

nitrogenous bases

stacked like rungs inside

leading strand

strand that is synthesized continuously in the 5'-3' direction, which is synthesized in the direction of the replication fork

primer

short stretch of nucleotides that is required to initiate replication; in the case of replication, the primer has RNA nucleotides

nucleotide excision repair

type of DNA repair mechanism in which the wrong base, along with a few nucleotides upstream or downstream, are removed

primase

enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA strand

lagging strand

during replication, the strand that is replicated in short fragments and away from the replication fork

Chapter 15

Genes and Proteins

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Summary

The genetic code is degenerate because 64 triplet codons in mRNA specify only 20 amino acids and three nonsense codons. In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template comprising two consensus sequences that recruit RNA polymerase. The genetic code refers to the DNA alphabet (A, T, C, G), the RNA alphabet (A, U, C, G), and the polypeptide alphabet (20 amino acids). The central dogma describes the flow of genetic information in the cell from genes to mRNA to proteins.

Key terms

consensus

DNA sequence that is used by many species to perform the same or similar functions

codon

three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation

core enzyme

prokaryotic RNA polymerase consisting of α , β , and β ' but missing σ ; this complex performs elongation

genetic code

degenerate because 64 triplet codons in mRNA specify only 20 amino acids and three nonsense codons

central dogma

states that genes specify the sequence of mRNAs, which in turn specify the sequence of proteins

promoter

DNA sequence to which RNA polymerase and associated factors bind and initiate transcription

nonsense codon

one of the three mRNA codons that specifies termination of translation

process of transcription; mRNA

used to synthesize proteins by the process of translation

Chapter 16

Gene Expression

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Summary

Gene expression in prokaryotes is mostly regulated at the transcriptional level (some epigenetic and post-translational regulation is also present), whereas in eukaryotic cells, gene expression is regulated at the… While all somatic cells within an organism contain the same DNA, not all cells within that organism express the same proteins. To express a protein, the DNA is first transcribed into RNA, which is then translated into proteins, which are then targeted to specific cellular locations. In eukaryotic cells, transcription occurs in the nucleus and is separate from the translation that occurs in the cytoplasm.

Key terms

gene expression

processes that control the turning on or turning off of a gene

DNA

first transcribed into RNA, which is then translated into proteins, which are then targeted to specific cellular locations

epigenetic

heritable changes that do not involve changes in the DNA sequence

post-translational

control of gene expression after a protein has been created

nucleus and

separate from the translation that occurs in the cytoplasm

5' cap

a methylated guanosine triphosphate (GTP) molecule that is attached to the 5' end of a messenger RNA to protect the end from degradation

catabolite activator protein (CAP)

protein that complexes with cAMP to bind to the promoter sequences of operons which control sugar processing when glucose is not available

enhancer

segment of DNA that is upstream, downstream, perhaps thousands of nucleotides away, or on another chromosome that influence the transcription of a specific gene

Chapter 17

Biotechnology and Genomics

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Summary

Medical professionals perform genetic testing to identify disease-causing genes, and use gene therapy to cure an inheritable disease Fragmented or whole chromosomes can separate on the basis of size by gel electrophoresis. The term “cloning” may refer to cloning small DNA fragments (molecular cloning), cloning cell populations (cellular cloning), or cloning entire organisms (reproductive cloning). Transgenic organisms possess DNA from a different species, usually generated by molecular cloning techniques.

Key terms

genomics

study of entire genomes including the complete set of genes, their nucleotide sequence and organization, and their interactions within a species and with other species

biotechnology

use of biological agents for technological advancement

recombinant DNA

combining DNA fragments that molecular cloning generates that do not exist in nature; also a chimeric molecule

gene therapy

technique used to cure inheritable diseases by replacing mutant genes with good genes

gel electrophoresis

technique used to separate molecules on the basis of size using electric charge

genetic testing

process of testing for the presence of disease-causing genes

cellular cloning

production of identical cell populations by binary fission

transgenic

organism that receives DNA from a different species

Chapter 18

Evolution and the Origin of Species

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Summary

Evolution is the process of adaptation through mutation, natural selection, and genetic drift which allows more desirable characteristics to pass to the next generation. For living organisms to adapt and change to environmental pressures, genetic variation must be present. With genetic variation, individuals have differences in form and function that allow some to survive certain conditions better than others. Evolution may be convergent with similar traits evolving in multiple species or divergent with diverse traits evolving in multiple species that came from a common ancestor.

Key terms

species

group of populations that interbreed and produce fertile offspring

natural selection

reproduction of individuals with favorable genetic traits that survive environmental change because of those traits, leading to evolutionary change

vestigial structure

physical structure present in an organism but that has no apparent function and appears to be from a functional structure in a distant ancestor

adaptation

heritable trait or behavior in an organism that aids in its survival and reproduction in its present environment

variation

genetic differences among individuals in a population

habitat isolation

reproductive isolation resulting when species' populations move or are moved to a new habitat, taking up residence in a place that no longer overlaps with the same species' other…

reproductive isolation

situation that occurs when a species is reproductively independent from other species; behavior, location, or reproductive barriers may cause this to happen

behavioral isolation

type of reproductive isolation that occurs when a specific behavior or lack of one prevents reproduction from taking place

Chapter 19

The Evolution of Populations

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Summary

The modern synthesis of evolutionary theory grew out of the cohesion of Darwin’s, Wallace’s, and Mendel’s thoughts on evolution and heredity, along with the more modern study of population genetics. It describes the evolution of populations and species, from small-scale changes among individuals to large-scale changes over paleontological time periods. To understand how organisms evolve, scientists can track populations’ allele frequencies over time. If they differ from generation to generation, scientists can conclude that the population is not in Hardy-Weinberg equilibrium, and is thus evolving

Key terms

modern synthesis

overarching evolutionary paradigm that took shape by the 1940s and scientists generally accept today

population genetics

study of how selective forces change the allele frequencies in a population over time

founder effect

event that initiates an allele frequency change in part of the population, which is not typical of the original population

frequency-dependent selection

selection that favors phenotypes that are either common (positive frequency-dependent selection) or rare (negative frequency-dependent selection)

geographical variation

differences in the phenotypic variation between populations that are separated geographically

assortative mating

when individuals tend to mate with those who are phenotypically similar to themselves

good genes hypothesis

theory of sexual selection that argues individuals develop impressive ornaments to show off their efficient metabolism or ability to fight disease

Chapter 20

Phylogenies and the History of Life

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Summary

Historically, scientists organized organisms into a taxonomic classification system. Each group of organisms went through its own evolutionary journey, or its phylogeny. However, today many scientists build phylogenetic trees to illustrate evolutionary relationships To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections between organisms.

Key terms

phylogenetic tree

diagram that reflects the evolutionary relationships among organisms or groups of organisms

phylogeny

evolutionary history and relationship of an organism or group of organisms

taxon

(plural: taxa) single level in the taxonomic classification system

class

division of phylum in the taxonomic classification system

analogy

(also, homoplasy) characteristic that is similar between organisms by convergent evolution, not due to the same evolutionary path

gene transfer agent (GTA)

bacteriophage-like particle that transfers random genomic segments from one species of prokaryote to another

genus

division of family in the taxonomic classification system; the first part of the binomial scientific name

rooted

single ancestral lineage on a phylogenetic tree to which all organisms represented in the diagram relate

Chapter 21

Viruses

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Summary

Viruses consist of a nucleic acid core surrounded by a protein capsid with or without an outer lipid envelope. The capsid shape, presence of an envelope, and core composition dictate some elements of the classification of viruses. Plant viruses may be transmitted either vertically from parent reproductive cells or horizontally through damaged plant tissues. Viruses are tiny, noncellular entities that usually can be seen only with an electron microscope.

Key terms

productive

viral infection that leads to the production of new virions

envelope

lipid bilayer that encircles some viruses

capsid

protein coating of the viral core

asymptomatic disease

disease where there are no symptoms and the individual is unaware of being infected unless lab tests are performed

lysogenic cycle

type of virus replication in which the viral genome is incorporated into the genome of the host cell

lytic cycle

type of virus replication in which virions are released through lysis, or bursting, of the cell

permissive

cell type that is able to support productive replication of a virus

prophage

phage DNA that is incorporated into the host cell genome

Chapter 22

Prokaryotes: Bacteria and Archaea

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Summary

During the first two billion years, the atmosphere was anoxic and only anaerobic organisms were able to live. Fossilized microbial mats are called stromatolites and consist of laminated organo-sedimentary structures formed by precipitation of minerals by prokaryotes. Cyanobacteria evolved from early phototrophs and began the oxygenation o the atmosphere. Hot springs and hydrothermal vents may have been the environments in which life began.

Key terms

phototroph

organism that is able to make its own food by converting solar energy to chemical energy

cyanobacteria

bacteria that evolved from early phototrophs and oxygenated the atmosphere; also known as blue-green algae

stromatolite

layered sedimentary structure formed by precipitation of minerals by prokaryotes in microbial mats

microbial mat

multi-layered sheet of prokaryotes that may include bacteria and archaea

hydrothermal vent

fissure in Earth’s surface that releases geothermally heated water

anaerobic

refers to organisms that grow without oxygen

aerobic

organisms that use oxygen

Chapter 23

Protists

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Summary

The oldest fossil evidence of eukaryotes is about 2 billion years old. Fossils older than this all appear to be prokaryotes. It is probable that today’s eukaryotes are descended from an ancestor that had a prokaryotic organization. The last common ancestor of today’s Eukarya had several characteristics, including cells with nuclei and an endomembrane system (which includes the nuclear envelope).

Key terms

oldest fossil evidence of eukaryotes

about 2 billion years old

biological carbon pump

process by which inorganic carbon is fixed by photosynthetic species that then die and fall to the sea floor where they cannot be reached by saprobes and their carbon dioxide…

plastid

one of a group of related organelles in plant cells that are involved in the storage of starches, fats, proteins, and pigments

cytoplasmic streaming

movement of cytoplasm into an extended pseudopod such that the entire cell is transported to the site of the pseudopod

test

porous shell of a foram that is built from various organic materials and typically hardened with calcium carbonate

mixotroph

organism that can obtain nutrition by autotrophic or heterotrophic means, usually facultatively

contractile vacuole

vesicle that fills with water (as it enters the cell by osmosis) and then contracts to squeeze water from the cell; an osmoregulatory vesicle

endosymbiosis

engulfment of one cell within another such that the engulfed cell survives, and both cells benefit; the process responsible for the evolution of mitochondria and chloroplasts in…

Chapter 24

Fungi

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Summary

Fungi can be unicellular as yeasts, or develop a network of filaments called a mycelium, which is often described as mold. Fungi that feed on decaying and dead matter are termed saprobes. External enzymes called exoenzymes digest nutrients that are absorbed by the body of the fungus, which is called a thallus. Fungi are eukaryotic organisms that appeared on land more than 450 million years ago, but clearly have an evolutionary history far greater.

Key terms

saprobe

organism that derives nutrients from decaying organic matter; also saprophyte

mold

tangle of visible mycelia with a fuzzy appearance

yeast

general term used to describe unicellular fungi

thallus

vegetative body of a fungus

mycorrhizae

a mutualistic relationship between a plant and a fungus. Mycorrhizae are connections between fungal hyphae, which provide soil minerals to the plant, and plant roots, which…

commensalism

symbiotic relationship in which one member benefits while the other member is not affected

heterothallic

describes when only one mating type is present in an individual mycelium

Chapter 25

Seedless Plants

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Summary

Charophytes form sporopollenin and precursors of lignin, phragmoplasts, and have flagellated sperm. Charophytes share more traits with land plants than do other algae, according to structural features and DNA analysis. Within the charophytes, the Charales, the Coleochaetales, and the Zygnematales have been each considered as sharing the closest common ancestry with the land plants. Land plants acquired traits that made it possible to colonize land and survive out of the water.

Key terms

charophyte

other term for green algae; considered the closest relative of land plants

lignin

complex polymer impermeable to water

sporopollenin

tough polymer surrounding the spore

non-vascular plant

plant that lacks vascular tissue, which is formed of specialized cells for the transport of water and nutrients

embryophyte

other name for land plant; embryo is protected and nourished by the sporophyte

gametangium

structure on the gametophyte in which gametes are produced

diplontic

diploid stage is the dominant stage

haplontic

haploid stage is the dominant stage

Chapter 26

Seed Plants

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Summary

In the gymnosperms, which appeared during the drier Permian period and became the dominant group during the Triassic, pollen was dispersed by wind, and their naked seeds developed in the sporophylls of a strobilus. Angiosperms bear both flowers and fruit. Seed plants appeared about 350 million years ago, during the Carboniferous period. Two major innovations were seeds and pollen.

Key terms

seed

structure containing the embryo, storage tissue, and protective coat

flower

underline branches end underline specialized for reproduction found in some seed-bearing plants, containing either specialized male or female organs or both male and female organs

strobilus

plant structure with a tight arrangement of sporophylls around a central stalk, as seen in cones or flowers; the male strobilus produces pollen, and the female strobilus produces…

fruit

thickened tissue derived from ovary wall that protects the embryo after fertilization and facilitates seed dispersal

gymnosperm

seed plant with naked seeds (seeds exposed on modified leaves or in cones)

barcoding

molecular biology technique in which one or more short gene sequences taken from a well-characterized portion of the genome is used to identify a species

dioecious

describes a species in which the male and female reproductive organs are carried on separate specimens

monoecious

describes a species in which the male and female reproductive organs are on the same plant

Chapter 27

Introduction to Animal Diversity

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Summary

A class of transcriptional control genes called Hox genes directs the organization of the major animal body plans, and these genes are strongly homologous across the animal kingdom The relationships between the Eumetazoa and more basal clades (Ctenophora, Porifera, and Placozoa) are still being debated. Although animals range in complexity from simple sea sponges to human beings, most members of the animal kingdom share certain features. Animals are eukaryotic, multicellular, heterotrophic organisms that ingest their food and usually develop into motile creatures with a fixed body plan.

Key terms

animal kingdom

the presence of differentiated tissues, such as nerve, muscle, and connective tissues, which are specialized to perform specific functions

Hox gene

(also, homeobox gene) master control gene that can turn on or off large numbers of other genes during embryogenesis

Eumetazoa

group of animals with true differentiated tissues

body plan

morphology or defining shape of an organism

Metazoa

group containing all animals

bilateral symmetry

type of symmetry in which there is only one plane of symmetry, so the left and right halves of an animal are mirror images

enterocoely

mesoderm of deuterostomes develops as pouches that are pinched off from endodermal tissue, cavity contained within the pouches becomes coelom

indeterminate cleavage

cleavage pattern in which individual blastomeres have the character of "stem cells," and are not yet predetermined to develop into specific cell types

Chapter 28

Invertebrates

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Summary

The mouth is surrounded by tentacles that contain large numbers of cnidocytes—specialized cells bearing nematocysts used for stinging and capturing prey as well as discouraging predators. Cnidarians represent a more complex level of organization than Porifera. Cnidarians possess a well-formed digestive system and carry out extracellular digestion in a digestive cavity that extends through much of the animal. Animals included in phylum Porifera are parazoans because they do not show the formation of true embryonically derived tissues, although they have a number of specific cell types and “functional” tissues such as…

Key terms

extracellular digestion

food is taken into the gastrovascular cavity, enzymes are secreted into the cavity, and the cells lining the cavity absorb nutrients

Cnidaria

phylum of animals that are diploblastic and have radial symmetry

mouth

surrounded by tentacles that contain large numbers of cnidocytes—specialized cells bearing nematocysts used for stinging and capturing prey as well as discouraging predat

nematocyst

harpoon-like organelle within cnidocyte with pointed projectile and poison to stun and entangle prey

spicule

structure made of silica or calcium carbonate that provides structural support for sponges

Porifera

phylum of animals with no true tissues, but a porous body with rudimentary endoskeleton

mesoglea

non-living, gel-like matrix present between ectoderm and endoderm in cnidarians

cnidocyte

specialized stinging cell found in Cnidaria

Chapter 29

Vertebrates

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Summary

Chordata contains two clades of invertebrates: Urochordata (tunicates) and Cephalochordata (lancelets), together with the vertebrates in the Vertebrata/Craniata. The five characteristic features of chordates present during some time of their life cycles are a notochord, a dorsal hollow tubular nerve cord, pharyngeal slits, endostyle/thyroid gland, and a post-anal tail. The name Craniata (organisms with a cranium) is considered to be synonymous with Vertebrata Most tunicates live on the ocean floor and are suspension feeders.

Key terms

notochord

flexible, rod-shaped support structure that is found in the embryonic stage of all chordates and in the adult stage of some chordates

hagfish

eel-like jawless fish that live on the ocean floor and are scavengers

tunicate

sessile chordate that is a member of Urochordata

Cephalochordata

chordate clade whose members possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail in the adult stage

Chordata

phylum of animals distinguished by their possession of a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some point during their development

Craniata

clade composed of chordates that possess a cranium; includes Vertebrata together with hagfishes

cranium

bony, cartilaginous, or fibrous structure surrounding the brain, jaw, and facial bones

post-anal tail

muscular, posterior elongation of the body extending beyond the anus in chordates

Chapter 30

Plant Form and Physiology

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Summary

A plant is composed of two main types of tissue: meristematic tissue and permanent tissue. A vascular plant consists of two organ systems: the shoot system and the root system. As growth occurs, meristematic tissue differentiates into permanent tissue, which is categorized as either simple or complex. The root system supports the plant and is usually underground.

Key terms

plant

composed of two main types of tissue: meristematic tissue and permanent tissue

permanent tissue

plant tissue composed of cells that are no longer actively dividing

shoot system

aboveground portion of the plant; consists of nonreproductive plant parts, such as leaves and stems, and reproductive parts, such as flowers and fruits

dermal tissue

protective plant tissue covering the outermost part of the plant; controls gas exchange

root system

belowground portion of the plant that supports the plant and absorbs water and minerals

ground tissue

plant tissue involved in photosynthesis; provides support, and stores water and sugars

meristematic tissue

tissue containing cells that constantly divide; contributes to plant growth

meristem

plant region of continuous growth

Chapter 31

Soil and Plant Nutrition

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Summary

Inorganic compounds form the majority of the soil solution. They are divided into macronutrients and micronutrients. The macronutrients plants require are carbon, nitrogen, hydrogen, oxygen, phosphorus, potassium, calcium, magnesium, and sulfur. The combination of organic compounds, along with water, carbon dioxide, and sunlight, produce the energy that allows plants to grow.

Key terms

soil

outer loose layer that covers the surface of Earth

macronutrient

nutrient that is required in large amounts for plant growth; carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur

inorganic compound

chemical compound that does not contain carbon; it is not part of or produced by a living organism

macronutrients plants require

carbon, nitrogen, hydrogen, oxygen, phosphorus, potassium, calcium, magnesium, and sulfur

micronutrient

nutrient required in small amounts; also called trace element

organic compound

chemical compound that contains carbon

C horizon

layer of soil that contains the parent material, and the organic and inorganic material that is broken down to form soil; also known as the soil base

mineral soil

type of soil that is formed from the weathering of rocks and inorganic material; composed primarily of sand, silt, and clay

Chapter 32

Plant Reproduction

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Summary

All complete flowers contain four whorls: the calyx, corolla, androecium, and gynoecium. The pollen contains two cells— a generative cell and a tube cell—and is covered by two layers called the intine and the exine. The female gametophyte is formed from mitotic divisions of the megaspore, forming an eight-nuclei ovule sac. The stamens are made up of anthers, in which pollen grains are produced, and a supportive strand called the filament.

Key terms

stamens

made up of anthers, in which pollen grains are produced, and a supportive strand called the filament

female gametophyte

formed from mitotic divisions of the megaspore, forming an eight-nuclei ovule sac

gametophyte

multicellular stage of the plant that gives rise to haploid gametes or spores

micropyle

opening on the ovule sac through which the pollen tube can gain entry

gynoecium

the sum of all the carpels in a flower

androecium

sum of all the stamens in a flower

exine

outermost covering of pollen

intine

inner lining of the pollen

Chapter 33

The Animal Body: Basic Form and Function

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Summary

The four primary tissues are epithelia, connective tissues, muscle tissues, and nervous tissues The basic building blocks of complex animals are four primary tissues. Animal bodies come in a variety of sizes and shapes. Limits on animal size and shape include impacts to their movement.

Key terms

four primary tissues

epithelia, connective tissues, muscle tissues, and nervous tissues

connective tissue

type of tissue made of cells, ground substance matrix, and fibers

columnar epithelia

epithelia made of cells taller than they are wide, specialized in absorption

pseudostratified

layer of epithelia that appears multilayered, but is a simple covering

fusiform

animal body shape that is tubular and tapered at both ends

cartilage

type of connective tissue with a large amount of ground substance matrix, cells called chondrocytes, and some amount of fibers

ventral cavity

body cavity on the anterior or front portion of an animal that includes the thoracic cavities and the abdominopelvic cavities

dorsal cavity

body cavity on the posterior or back portion of an animal; includes the cranial and vertebral cavities

Chapter 34

Animal Nutrition and the Digestive System

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Summary

Ruminants that consume large amounts of plant material have a multi-chambered stomach that digests roughage. Humans and many other animals have monogastric digestive systems with a single-chambered stomach. Birds have evolved a digestive system that includes a gizzard where the food is crushed into smaller pieces. Pseudo-ruminants have similar digestive processes as ruminants but do not have the four-compartment stomach.

Key terms

roughage

component of food that is low in energy and high in fiber

digestion

mechanical and chemical breakdown of food into small organic fragments

monogastric

digestive system that consists of a single-chambered stomach

ruminant

animal with a stomach divided into four compartments

stomach

saclike organ containing acidic digestive juices

gizzard

muscular organ that grinds food

gizzard where the food

crushed into smaller pieces

Chapter 35

The Nervous System

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Summary

The nervous system is made up of neurons and glia. Most neurons contain dendrites, which receive these signals, and axons that send signals to other neurons or tissues. Glia are non-neuronal cells in the nervous system that support neuronal development and signaling. Neurons are specialized cells that are capable of sending electrical as well as chemical signals.

Key terms

nervous system

made up of neurons and glia

axon

tube-like structure that propagates a signal from a neuron’s cell body to axon terminals

dendrite

structure that extends away from the cell body to receive messages from other neurons

neuron

specialized cell that can receive and transmit electrical and chemical signals

glia

(also, glial cells) cells that provide support functions for neurons

basal ganglia

interconnected collections of cells in the brain that are involved in movement and motivation; also known as basal nuclei

refractory period

period after an action potential when it is more difficult or impossible for an action potential to be fired; caused by inactivation of sodium channels and activation of…

temporal lobe

part of the cerebral cortex that processes auditory input; parts of the temporal lobe are involved in speech, memory, and emotion processing

Chapter 36

Sensory Systems

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Summary

A sensory activation occurs when a physical or chemical stimulus is processed into a neural signal (sensory transduction) by a sensory receptor. Humans have special senses: olfaction, gustation, equilibrium, and hearing, plus the general senses of somatosensation Each sensory receptor is responsive to stimuli within a specific region in space, which is known as that receptor’s receptive field. Perception is an individual interpretation of a sensation and is a brain function.

Key terms

sensory receptor

specialized neuron or other cells associated with a neuron that is modified to receive specific sensory input

sensory transduction

conversion of a sensory stimulus into electrical energy in the nervous system by a change in the membrane potential

physical or chemical stimulus

processed into a neural signal (sensory transduction) by a sensory receptor

receptive field

region in space in which a stimulus can activate a given sensory receptor

perception

individual interpretation of a sensation; a brain function

cone

weakly photosensitive, chromatic, cone-shaped neuron in the fovea of the retina that detects bright light and is used in daytime color vision

Chapter 37

The Endocrine System

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Summary

Hormones can affect cells directly through intracellular hormone receptors or indirectly through plasma membrane hormone receptors Amino acid-derived hormones are relatively small molecules and include the adrenal hormones epinephrine and norepinephrine. Peptide hormones are polypeptide chains or proteins and include the pituitary hormones, antidiuretic hormone (vasopressin), and oxytocin Lipid-derived hormones are structurally similar to cholesterol and include steroid hormones such as estradiol and testosterone.

Key terms

oxytocin

hormone released by the posterior pituitary to stimulate uterine contractions during childbirth and milk let-down in the mammary glands

norepinephrine

hormone released by the adrenal medulla in response to a short-term stress hormone production by the gonads

epinephrine

hormone released by the adrenal medulla in response to a short term stress

plasma membrane hormone receptor

a hormone receptor on the surface of the plasma membrane of a cell

intracellular hormone receptor

a hormone receptor in the cytoplasm or nucleus of a cell

hormone receptor

the cellular protein that binds to a hormone

lipid-derived hormone

hormone derived mostly from cholesterol

peptide hormone

hormone composed of a polypeptide chain

Chapter 38

The Musculoskeletal System

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Summary

The axial skeleton is composed of the bones of the skull, ossicles of the ear, hyoid bone, vertebral column, and ribcage. The human skeleton is an endoskeleton that is composed of the axial and appendicular skeleton. The skull consists of eight cranial bones and 14 facial bones. The three types of skeleton designs are hydrostatic skeletons, exoskeletons, and endoskeletons.

Key terms

human skeleton

an endoskeleton that is composed of the axial and appendicular skeleton

appendicular skeleton

composed of the bones of the upper limbs, which function to grasp and manipulate objects, and the lower limbs, which permit locomotion

axial skeleton

forms the central axis of the body and includes the bones of the skull, the ossicles of the middle ear, the hyoid bone of the throat, the vertebral column, and the thoracic cage…

cranial bone

one of eight bones that form the cranial cavity that encloses the brain and serves as an attachment site for the muscles of the head and neck

facial bone

one of the 14 bones that form the face; provides cavities for the sense organs (eyes, mouth, and nose) and attachment points for facial muscles

rib

one of 12 pairs of long, curved bones that attach to the thoracic vertebrae and curve toward the front of the body to form the ribcage

vertebral column

(also, spine) surrounds and protects the spinal cord, supports the head, and acts as an attachment point for ribs and muscles of the back and neck

exoskeleton

a secreted cellular product external skeleton that consists of a hard encasement on the surface of an organism

Chapter 39

The Respiratory System

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Summary

The respiratory bronchioles open into the alveolar ducts, alveolar sacs, and alveoli. Air then travels down the pharynx, through the trachea, and into the lungs. In the lungs, air passes through the branching bronchi, reaching the respiratory bronchioles, which house the first site of gas exchange. These include the hair and mucus in the nasal cavity that trap dust, dirt, and other particulate matter before they can enter the system.

Key terms

respiratory bronchiole

terminal portion of the bronchiole tree that is attached to the terminal bronchioles and alveoli ducts, alveolar sacs, and alveoli

particulate matter

small particle such as dust, dirt, viral particles, and bacteria that are in the air

pharynx

throat; a tube that starts in the internal nares and runs partway down the neck, where it opens into the esophagus and the larynx

mucus

sticky protein-containing fluid secretion in the lung that traps particulate matter to be expelled from the body

trachea

cartilaginous tube that transports air from the larynx to the primary bronchi

alveolar sac

structure consisting of two or more alveoli that share a common opening

bronchiole

airway that extends from the main tertiary bronchi to the alveolar sac

alveolar duct

duct that extends from the terminal bronchiole to the alveolar sac

Chapter 40

The Circulatory System

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Summary

Circulatory systems may be open (mixed with the interstitial fluid) or closed (separated from the interstitial fluid). Closed circulatory systems are a characteristic of vertebrates; however, there are significant differences in the structure of the heart and the circulation of blood between the different vertebrate groups due to… In most animals, the circulatory system is used to transport blood through the body. However, complex organisms use the circulatory system to carry gases, nutrients, and waste through the body.

Key terms

circulatory system

used to transport blood through the body

closed circulatory system

system in which the blood is separated from the bodily interstitial fluid and contained in blood vessels

double circulation

flow of blood in two circuits: the pulmonary circuit through the lungs and the systemic circuit through the organs and body

unidirectional circulation

flow of blood in a single circuit; occurs in fish where the blood flows through the gills, then past the organs and the rest of the body, before returning to the heart

gill circulation

circulatory system that is specific to animals with gills for gas exchange; the blood flows through the gills for oxygenation

lymph node

specialized organ that contains a large number of macrophages that clean the lymph before the fluid is returned to the heart

red blood cell

small (7-8 μm) biconcave cell without mitochondria (and in mammals without nuclei) that is packed with hemoglobin, giving the cell its red color; transports oxygen through the body

Chapter 41

Osmotic Regulation and Excretion

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Summary

It is the number of solute molecules and not the molecular size that is important in osmosis. Osmoregulation and osmotic balance are important bodily functions, resulting in water and salt balance. Osmosis occurs to equalize the number of solute molecules across a semi-permeable membrane by the movement of water to the side of higher solute concentration. Osmolarity is measured in units of milliequivalents or milliosmoles, both of which take into consideration the number of solute particles and the charge on them.

Key terms

osmoregulation

mechanism by which water and solute concentrations are maintained at desired levels

osmotic balance

balance of the amount of water and salt input and output to and from a biological system without disturbing the desired osmotic pressure and solute concentration in every…

semi-permeable membrane

membrane that allows only certain solutes to pass through

mole

gram equivalent of the molecular weight of a substance

molarity

number of moles of solute per liter of solution

countercurrent multiplier

osmotic gradient in the renal medulla that is responsible for concentration of urine

distal convoluted tubule (DCT)

part of the renal tubule that is the most distant from the glomerulus

Chapter 42

The Immune System

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Summary

Using a combination of cellular and molecular attacks, the innate immune system identifies the nature of a pathogen and responds with inflammation, phagocytosis, cytokine release, destruction by NK cells, and/or a… T H cells stimulate B cells that have engulfed and presented pathogen-derived antigens. APCs display antigens via MHC molecules to complementary naïve T cells. The innate immune system serves as a first responder to pathogenic threats that bypass natural physical and chemical barriers of the body.

Key terms

cytokine

chemical messenger that regulates cell differentiation, proliferation, gene expression, and cell trafficking to effect immune responses

inflammation

localized redness, swelling, heat, and pain that results from the movement of leukocytes and fluid through opened capillaries to a site of infection

T cell

lymphocyte that matures in the thymus gland; one of the main cells involved in the adaptive immune system

B cell

lymphocyte that matures in the bone marrow and differentiates into antibody-secreting plasma cells

pathogen

an agent, usually a microorganism, that causes disease in the organisms that it invades

antigen

foreign or “non-self” protein that triggers the immune response

complement system

array of approximately 20 soluble proteins of the innate immune system that enhance phagocytosis, bore holes in pathogens, and recruit lymphocytes; enhances the adaptive response…

Chapter 43

Animal Reproduction and Development

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Summary

Asexual reproduction occurs through fission, budding, and fragmentation. Reproduction may be asexual when one individual produces genetically identical offspring, or sexual when the genetic material from two individuals is combined to produce genetically diverse offspring. Sexual reproduction may mean the joining of sperm and eggs within animals’ bodies or it may mean the release of sperm and eggs into the environment. Sexual reproduction starts with the combination of a sperm and an egg in a process called fertilization.

Key terms

asexual reproduction

form of reproduction that produces offspring that are genetically identical to the parent

budding

form of asexual reproduction that results from the outgrowth of a part of a cell leading to a separation from the original animal into two individuals

fission

(also, binary fission) method by which multicellular organisms increase in size or asexual reproduction in which a unicellular organism splits into two separate organisms by…

fragmentation

cutting or fragmenting of the original animal into parts and the growth of a separate animal from each part

sexual reproduction

mixing of genetic material from two individuals to produce genetically unique offspring

genetic material from two individuals

combined to produce genetically diverse offspring

estradiol

most potent form of estrogen that is responsible for the development of female secondary female characteristics, maintenance of female reproductive organs, and preparation for…

oviparity

process by which fertilized eggs are laid outside the female’s body and develop there, receiving nourishment from the yolk that is a part of the egg

Chapter 44

Ecology and the Biosphere

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Summary

Biogeography is the study of the geographic distribution of living things as well as the abiotic factors that affect their distribution. Ecologists studying an ecosystem examine the living species (the biotic components) of the ecosystem as well as the nonliving portions (the abiotic components), such as air, water, and soil, of the environment Ecology is the study of the interactions of living things with their environment. Endemic species are species that are naturally found only in a specific geographic area.

Key terms

ecology

study of interaction between living things and their environment

distribution of living things

influenced by several environmental factors that are, in part, controlled by the latitude or elevation at which a species is found

endemic

species found only in a specific geographic area that is usually restricted in size

biogeography

study of the geographic distribution of living things and the abiotic factors that affect their distribution

abiotic

nonliving components of the environment

biotic

living components of the environment

biome

ecological community of plants, animals, and other organisms that is adapted to a characteristic set of environmental conditions

emergent vegetation

wetland plants that are rooted in the soil but have portions of leaves, stems, and flowers extending above the water’s surface

Chapter 45

Population and Community Ecology

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Summary

Ecologists measure characteristics of populations: size, density, dispersion pattern, age structure, and sex ratio. Life tables are useful to calculate life expectancies of individual population members. Survivorship curves show the number of individuals surviving at each age interval plotted versus time All species have evolved a pattern of living, called a life history strategy, in which they partition energy for growth, maintenance, and reproduction.

Key terms

ecology

the study of the relationships among living organisms and their environment

life history

inherited pattern of resource allocation under the influence of natural selection and other evolutionary forces

survivorship curve

graph of the number of surviving population members versus the relative age of the member

life table

table showing the life expectancy of a population member based on its age

age structure

proportion of population members at specific age ranges

fecundity

potential reproductive capacity of an individual

climax community

final stage of succession, where a stable community is formed by a characteristic assortment of plant and animal species

commensalism

relationship between species wherein one species benefits from the close, prolonged interaction, while the other species neither benefits nor is harmed

Chapter 46

Ecosystems

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Summary

Analytical models are used to describe linear food chains, and simulation models work best with holistic food webs Organisms in an ecosystem acquire energy in a variety of ways, which is transferred between trophic levels as the energy flows from the bottom to the top of the food web, with energy being lost at each transfer. Modeling of ecosystem energy is best done with ecological pyramids of energy, although other ecological pyramids provide other vital information about ecosystem structure Ecosystems exist on land, at sea, in the air, and underground.

Key terms

ecosystem

community of living organisms and their interactions with their abiotic environment

analytical model

ecosystem model that is created with mathematical formulas to predict the effects of environmental disturbances on ecosystem structure and dynamics

simulation model

ecosystem model that is created with computer programs to holistically model ecosystems and to predict the effects of environmental disturbances on ecosystem structure and dynamics

conceptual model

(also, compartment model) ecosystem model that consists of flow charts that show the interactions of different compartments of the living and nonliving components of the ecosystem

ecological pyramid

(also, Eltonian pyramid) graphical representation of different trophic levels in an ecosystem based of organism numbers, biomass, or energy content

food chain

linear representation of a chain of primary producers, primary consumers, and higher-level consumers used to describe ecosystem structure and dynamics

food web

graphic representation of a holistic, nonlinear web of primary producers, primary consumers, and higher-level consumers used to describe ecosystem structure and dynamics

efficiency of these transfers

important for understanding the different behaviors and eating habits of warm-blooded versus cold-blooded animals

Chapter 47

Conservation Biology and Biodiversity

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Summary

These measurements include numbers of species, genetic diversity, chemical diversity, and ecosystem diversity. Biodiversity recovery times after mass extinctions vary, but may be as long as 30 million years. Biodiversity exists at multiple levels of organization and is measured in different ways depending on the scientific goals of those taking the measurements. The number of described species is estimated to be 1.5 million with about 17,000 new species being described each year.

Key terms

biodiversity

variety of a biological system, typically conceived as the number of species, but also applying to genes, biochemistry, and ecosystems

extinction

disappearance of a species from Earth; local extinction is the disappearance of a species from a region

genetic diversity

variety of genes in a species or other taxonomic group or ecosystem, the term can refer to allelic diversity or genome-wide diversity

number of described species

estimated to be 1.5 million with about 17,000 new species being described each year

chemical diversity

variety of metabolic compounds in an ecosystem

secondary plant compound

compound produced as byproducts of plant metabolic processes that is usually toxic, but is sequestered by the plant to defend against herbivores