Ap Bio Chapter 22 Outline - Evolution­ D?escent with Modification or a Change in the Genetic Composition of a Population from Generation to Generation

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with Darwin’s theory.

(2) To Darwin, the Linnaean hierarchy reflected the branching history of the tree of life.

(a) Organisms at various taxonomic levels are united through descent from common ancestors.

(b)

d) Evolutionary biologist Ernst Mayr has dissected the logic of

Darwin’s theory into three inferences based on five observations.

(1) Observation #1:​All species have such great potential

fertility that their population size would increase exponentially if all individuals that are born reproduced successfully.

(2) Observation #2:​Populations tend to remain stable in size, except for seasonal fluctuations.

(a) Inference #1:​Production of more individuals than the environment can support leads to a struggle for existence among the individuals of a population, with only a fraction of the offspring surviving each generation.

(b) Inference #2:​Survival in the struggle for existence is not random, but depends in part on inherited traits. Those individuals whose inherited traits are best suited for survival and reproduction in their environment are likely to leave more offspring than less fit individuals.

III. Evolution is supported by an overwhelming amount of scientific evidence A. Directobservationsofevolutionarychange

1. Natural Selection in response to introduced plant species

a) Animals that eat plants often have specific adaptations for that

plant

(1) Soapberry bugs use a specific beak to feed on seed plants

(a) based on their location determines what type of beak the bug has for food

2. Evolution of Drug­ Resistant Bacteria

a) certain bacteria on humans were harmful, but the good bacteria

B. Homology

took over and eventually they were able to fight off the bad bacteria.

(1) penicillin

1. Homology

a) similarity resulting from common ancestry

(1) For example, the forelimbs of human, cats, whales, and

bats share the same skeletal elements, even though the

appendages have very different functions.

(2) These forelimbs are homologous structures that represent

variations on the ancestral tetrapod forelimb.

2. Anatomical and Molecular Homologies

a) Homologous Structures

(1) variations on a structural theme that was present in a common ancestor

(a) comparing early stages of development in different animal species reveals additional anatomical homologies not visible in adult organism’s

b) VestigialStructures

(1) remnants of features that served a function in an organism’s ancestors

(a) some snakes have pelvises and leg bones

c) Evolutionary Tree

(1) a diagram that reflects evolutionary relationships among organsims

3. The Fossil Record

a) The succession of fossil forms is consistent with what is known

from other types of evidence about the major branches of descent in the tree of life.

(1) evidence suggests that prokaryotes are the ancestors of all life and should precede all eukaryotes in the fossil record. In fact, the oldest known fossils are prokaryotes.

(2) Fossil fishes predate all other vertebrates, with amphibians next, followed by reptiles, then mammals and birds.

(3) This is consistent with the history of vertebrate descent supported by many other types of evidence.

b) The Darwinian view of life also predicts that evolutionary transitions should leave signs in the fossil record.

c) Paleontologists have discovered fossils of many such transitional forms that link ancient organisms to modern species.

(1) fossil evidence documents the origin of birds from one branch of dinosaurs.

(2) Recent discoveries include fossilized whales that link these aquatic mammals to their terrestrial ancestors.

4. Biogeography

a) Biogeography

(1) the geographic distribution of species

b) Pangaea

(1) the united area of all of earth’s land masses about 250 million years ago

1.B

2.D

3.D

4.C

5.A

c) This type of knowledge is useful to track the remains and origins of fossils and other types