Theory of Evolution

Identify evidence of change in species using DNA sequences, anatomical similarities, physiological similarities, embryology and fossils

Illustrate the results of natural selection (changes) in speciation, diversity, phylogeny, adaptation, behavior and extinction

Evolution Evolution: change in the traits of a species over time Species: a group of organisms who can produce fertile

offspring Charles Darwin: developed the theory of evolution called

Natural Selection Natural Selection states that:

there is variation (differences) within populations some variations are favorable (favorable variations

improve an organism’s ability to function and reproduce in its own environment)

not all young produced in each generation can survive individuals that survive and reproduce are those with

favorable variations; these individuals can then pass on the favorable traits to their offspring

Evidence to Support Evolution: DNA: by comparing the DNA sequences of two organisms or the amino acid

sequences made from the DNA, scientists can learn which organisms are related; the more DNA two organisms have in common, the closer related they are

•Using the table, compare the amino acid sequence of the chimp and the human.

•Notice that for this protein the chimp and human have the exact same sequence.

•Now compare the baboon and the human.

•Notice that there are 5 differences in the sequence.

•This tells you that the human is more closely related to the chimp than the baboon.

Anatomical similarities An inherited trait that increases the

population’s chances of survival and reproduction is an adaptationhomologous structure: same structure

with different functions found in different species and thought to be inherited from common ancestors

ex: humans, whales, and bats all have the same # and type of bones in the forelimbs but their functions are different

Analogous structures have the same function, but different structures & do not show a close relationship

ex: insect wing and bird's wing

Embryology Similarity in embryo development shows a close

relationship (vertebrate embryos all have tail & gill slits)

Fossils

These are imprints or remains of living things.

In undisturbed layers of sedimentary rock, the deeper it is, the older it is.

Give us information about extinct species.

Adaptation mimicry: an organism can copy the appearance of

another organism; in one form of mimicry, a harmless species has adaptations that result in a physical resemblance to a harmful species; predators that avoid the harmful looking species also avoid the similar-looking harmless species.

camouflage: an organism can blend into the surroundings

Variation

the differences between individual members of a population (ex: fur color, eye color, etc.)

cannot always be observed are almost always genetically inherited results from mutations and recombination

Speciation Speciation: the evolution of a new species

when the production of fertile offspring in a species is somehow prevented; it can occur in several ways:

Geographic Isolation: physical barriers separate members of a population so that they can not reproduce; these barriers can be caused by changes in climate, volcanic eruptions, or changes in sea level; the separate groups become more and more distinct and eventually become separate species

Polyploids: mistakes in meiosis cause the chromosome number in individuals to change; when a polyploidy organism mates with a normal individual, the zygotes do not develop normally; this type of speciation is more common in plants

Speciation

new species

species

original species

Types of Evolution:

adaptive radiation: when a species is introduced to a new environment, several new species evolve

convergent evolution: distantly related organisms evolve similar traits

directional selection: occurs when natural selection favors one of the extreme variations of a trait.

disruptive selection: individuals with either extreme of a trait’s variation are selected for

Adaptive Radiationnew species

new species

species new species

new species

new species

Convergent Evolution

species new speciesnew species

species

these 2 new species share many traits

Directional vs. Disruptive Selection In directional selection, there is a shift in

frequency to an extreme phenotype. In the example, the environment was changed so that now it is barren and has dark soil.

rabbit coat color

light medium dark

Directional vs. Disruptive Selection

In disruptive selection, the most common variation in a population is not favored. In the example, light-colored bushes have begun to grow in the dark soil.

rabbit coat color

light medium dark

Phylogeny Phylogeny: the evolutionary history of an

organism; this is used to classify organisms into kingdoms, phyla, classes, etc.; a phylogenetic tree or cladogram shows how organisms are related to one another and how they evolved

examples of phylogenetic trees

Behavior Behavior: anything an animal does in response to a

stimulus; types of behaviors include: innate behaviors: inherited behaviors reflex: simple innate behavior that is automatic (don’t

need to think about it) instinct: complex pattern of innate behaviors that begins

when an animal recognizes a stimulus and continues until all parts of the behavior have been completed

territorial behavior: behavior in which animals will defend their space by driving away others of the same species

aggression: behavior that is used to intimidate another animal of the same species

Extinction

A population is extinct when the last of that species is dead.

Example: There are no more dinosaurs. What happened? Their habitat was destroyed. When

they no longer have what they need to live, they die.