Chapter 27 (A)

Question 1

gene flow

Answer 1

is the movement of alleles between populations.

Gene flow mixes genetic diversity.

Gene flow also keeps the gene pools of two or more populations similar.

Question 2

Geological timescale as evidence for evolution

Answer 2

History of Earth is divided into eras, periods, and then epochs.
> Fossil record has helped determine the dates.

Two methods are used: Relative dating method & Absolute method

Question 3

Biochemical evidence for evolution

Answer 3

Evolution is a theory, supported by a large number of observations and experiments

Almost all organisms use the same basic biochemical molecules, including DNA, ATP, and many enzymes.
> Organisms use the same DNA triplet code for the same 20 amino acids in their proteins.
> Humans share many genes with much simpler organisms.
> The diversity of life is due to only a slight difference in many of the same genes.
> The more similar the DNA sequences, the more closely related the organisms are.

Question 4

gene pool

Answer 4

the sum total of all alleles of all genes in a population.

Question 5

Relative dating method

Answer 5

Determines the relative order of fossils and strata but not the actual date.

Question 6

transitional link

Answer 6

Some fossils serve as transitional links between groups.
> Fossils of Archaeopteryx that lived 165 million years ago serve as an example.
>They display an intermediate form between dinosaurs and birds.
> The fossils of Archaeopteryx are similar to other transitional fossils in that they have some traits like their ancestors and others like their descendants, rather than intermediate traits.

Question 7

founder effect

Answer 7

occurs when a few individuals form a new colony and their collective genes represent only a fraction of the original gene pool.

Question 8

vestigial structures

Answer 8

Anatomical structures fully functional in one group and reduced or nonfunctional in another.

Example: snakes have no use for hindlimbs, and yet some have remnants of hindlimbs in pelvic girdle and leg.

Question 9

mutations

Answer 9

are genetic changes that are the only source of new variation in a population.

New mutations can cause allele frequencies in a population to change.

Without mutations, there would be no new inheritable genetic diversity.

Mutations are random events.

Some are beneficial (provide a survival advantage), and some are harmful.

Question 10

Fossil evidence for evolution

Answer 10

Fossils are remains and traces of past life or any other direct evidence of past life.
> Hard body parts most often preserved: shells, bones, teeth.
»Soft parts can be buried quickly so decomposition is never completed.
>Traces include footprints, burrows, casts.
>Majority of fossils embedded in sedimentary rock.
>Deposited in layers called strata.

Some fossils serve as transitional links between groups.

Fossils of Ambulocetus natans suggest that whales had a terrestrial ancestor.

Question 11

The five conditions of Hardy-Weinberg Equilibrium and the corresponding deviations from the condition (Table 27.2)

Answer 11

No mutations - mutation

No genetic drift - genetic drift (bottleneck & founder effect)

No migration (gene flow) - immigration/emigration

Random mating - nonrandom mating

No selection - selection

Question 12

theory of natural selection

Answer 12

Individual organisms in a species exhibit variation that can be passed from one generation to the next.
> Heritable variation.

Organisms compete for available resources.
> Malthus essay that population growth is kept in check due to limits of environment.

Individual organisms within a population differ in terms of their reproductive success.
> Some individuals in a population have favorable traits that enable them to better compete for limited resources.
» Can devote more energy to reproduction and have more offspring.

Organisms become adapted to conditions as the environment changes.
> Natural selection through differential reproductive success shapes traits.
> The result of this descent with modification is adaptation.

Question 13

Absolute method

Answer 13

Radioactive dating techniques are used to assign an actual date to a fossil.

Technique is based on the half-life of radioactive isotopes.

Question 14

microevolution

Answer 14

is the change in allele frequencies in a population over time.

Question 15

Natural Selection

Answer 15

is a process that allows some individuals with an advantage over others to produce more offspring.

Main Types:
stabilizing
directional
disruptive

Question 16

adaptation

Answer 16

Darwin called the process of adaptation “evolution by natural selection.”

Any evolved trait that helps an organism be more suited to its environment.

Question 17

population

Answer 17

all members of a species occupying a particular area at the same time and that interbreed and exchange genes.

Question 18

homologous structure

Answer 18

Anatomically similar because they are inherited from a common ancestor.

Example: human arm and whale forelimb.

Question 19

continental drift

Answer 19

The positions of continents and oceans have shifted through time.

The distribution of fossils and existing species provides evidence of former positions of continents.

Question 20

bottleneck affect

Answer 20

occurs following a natural disaster that kills a large proportion of a population.

Question 21

Evolution

Answer 21

is all the changes that have occurred in living organisms due to differential reproductive success in living organisms over geological time.

Question 22

Lamark’s proposal of the inheritance of acquired characteristics

Answer 22

The environment can bring about an inherited change

Epigenetic inheritance: chemical modifications to the DNA that occur in one generation may be passed on to later generations.

Question 23

genetic drift

Answer 23

is a change in allele frequencies of a gene pool due to random meeting of gametes in fertilization.

Genetic drift has greater effects in smaller populations due to fewer gametes assorting.

Bottleneck and Founder Effect

Question 24

embryological development structure

Answer 24

At some time in development, all vertebrates have a tail and paired pharyngeal pouches.

Reflects common ancestry.

Question 25

Hardy-Weinberg Equilibrium describes a population in which allele frequencies do not change over time which are never achieved in wild populations.

Answer 25

Allele frequencies in a gene pool will remain at equilibrium, thus constant, in each generation of a large, sexually reproducing population as long as the five conditions are met

Hardy and Weinberg used the equation: p2 + 2pq + q2 to describe the genotype and allele frequencies in a population.
> p2 = frequency of DD genotype.
> 2pq = frequency of Dd genotype.
> q2 = frequency of dd genotype.

Question 26

theory of evolution

Answer 26

Charles Darwin

This process, called evolution, proposes that species arise, change, and become extinct due to natural, not supernatural forces.

Darwin’s theory of evolution by natural selection explains both the unity and diversity of life on Earth.
> How all living organisms share a common ancestor.
> How species adapt to various habitats and ways of life.

Question 27

allele frequency

Answer 27

the proportion of each allele in a population’s gene pool.

Question 28

analogous structures

Answer 28

Serve the same function but not constructed similarly and do not share a common ancestry.

Example: wing of bird and wing of an insect.

Question 29

Biogeographical evidence for evolution

Answer 29

The first cells evolved in water.

Organisms are composed of 70% to 90% water.

Water is a polar molecule.

Water molecules form hydrogen bonds, which cause them to cling to one another.

Question 30

Anatomical evidence for evolution and structures (4)

Answer 30

Common descent offers explanation for anatomical similarities among organisms.

homologous
vestigial
embryological
analogous