Chapter 22: Evolution by Natural Selection (Exam 1)

Plato's view

Typological Thinking -- Every organism is a type, no variation, perfect essence from God

Aristole's view

Typological Thinking & Scale of Nature -- Organisms are sequenced based on increasing size & complexity. plants -> humans. Surpassed by angles and God. Popular in 1700s

Lamarck's Views

Change thru time & Scale of Nature -- 1809; simple organisms evolve into more complex ones (plants evolve into worms, worms 2 fish, & so on)

Darwin & Wallace's views

Change thru time & Common Ancestry -- Everything is related by common ancestors, no types; lives in population

Fossils

Traces of organisms that lived in the past

How are fossils organized according to their relative ages?

By observing the rock layers

Geologic Time Scale

Based on fossils' relative positions in layers

of sedimentary rock. Geologic time is divided

into eons, eras, periods, and epochs

What does extinction tell us about past life?

Species are dynamic; #'s and types have changed over time, over 99% of species that have lived are extinct, extinctions have occured continously in earth's history

Transitional forms

Traits in fossil species that are intermediate between ancestral and derived species

Vestigial Traits

A reduced or incompletely developed structure in an organism that has no (or reduced) function

Clearly similar to functioning organs or structures in closely related species

Homology vs Homoplasy

Characteristic shared in species that was present in common ancestor vs not

Genetic Homology

With minor exceptions, all organisms use the same rules for transferring information coded in DNA into proteins

Developmental Homology

Similarity in developmental structures or processes

Structural Homology

Similarity in adult morphology

Supporting ideas that species have descended

The fossil record (unique ear bones) & its phylogeny (can see transition between terrestrial & aquatic forms)

Darwin's 4 Postulates

1. Variation exists among individual organisms that make up a

population

2. Some of the trait differences are heritable (passed onto offspring)

3. Survival and reproductive success are highly variable

4. The survival and reproduction of individuals are not random

a. the individuals who survive and go on to reproduce the most are

those with the most favorable variation, and they are naturally

selected

When does evolution by NS occur?

Heritable variation leading to differential reproductive success

Evolutionary Fitness

Ability of an individual to produce surviving, fertile offspring relative to that ability in other individuals in population

How did the finche's beak size influence reproductive success?

Since most small seeds gone, the smaller beak birds died. This caused the larger beak birds to reproduce making their population rapidly increase

Fitness Trade-Offs

Compromise between traits, in terms of how those traits perform in the environment.

Because selection acts on many traits at once, every adaptation is a compromise

(bright coloration & tendency to attract predators)

Pleiotropy

A single allele affects multiple traits (all mammals having 7 cervical vertebrae)

How can a lack of genetic variation constrain evolution?

NS can only work on existing variations in populations

How are traits historically & environmentally constrained