Evidence of Evolution

Evidence of Evolution

1. The Fossil Record- ch 142. Geographic

Distribution of Living Things-similar environments have similar types of organisms

3. Body Structures a) Homologous, b) analogous,c) vestigial

4. Similarities in Early Development


Homologous Structures

Analogous Structures

• Body part in different species that is similar in function but not in structure

• that evolved in response to a similar environmental challenge

Evidence for Evolution• Vestigial organs-

organs that serve no useful function in an organism

• i.e.) appendix, miniature legs, arms


Similarities in Early

Development

• Same • DNA & processes• Comparative

embryology

Lamarackacquired traits

can be inherited

He believed that over the lifetime of an individual, physical features increased in size b/c of use or

reduce in size b/c of disuse.He also believed these changes were then passed on

to offspringONLY OCCURS IF IT IS CAUSED BY A MUTATION

Hypothesis of Acquired Characteristics

• In 1809, Jean Baptiste de Lamarck suggested that characteristics, or traits, developed during a parent organism’s lifetime are inherited by its offspring.

• His hypothesis is called the inheritance of acquired characteristics.

• Scientists collected data on traits that are passed from parents to offspring.

• The data showed that traits developed during a parent’s lifetime, such as large muscles built by hard work or exercise, are not passed on to offspring.

• The evidence did not support Lamarck’s hypothesis.

Mutations

are the only way new traits can appear?

• In December 1831, Charles Darwin recorded observations about the plants and animals he saw on the South American coast.

Darwin’s Model of EvolutionIdeas About Evolution

1

Adaptive Radiationthe diversification of an ancestral group of organisms into a variety ofrelated forms speciali

zed to fit different environments or ways of life

• Darwin hypothesised evolution, that the different

species of Galapagos finches descended from

mainland finches that had reached the islands

sometime in the past. Over time they evolved and

gradual changes occurred to the island finches.

Eventually they were different enough from the

mainland finches to be considered a new

species. Darwin proposed the island had become

inhabited by many different but related species of

finches. -

Main Idea

• Charles Darwin- natural selection describes the unequal survival & reproduction that results from the presence or absence of particular traits

• It is responsible for evolution• Selecting and breeding for specific traits is evolution

by artificial selection• We have unintentionally selected for pests that are

resistant to pesticides and for bacteria that are resistant to antibiotics

Natural Selection• Charles Darwin collected

more evidence on inherited traits by breeding racing pigeons.

• He also studied breeds of dogs and varieties of flowers. In the mid 1800s,

• Darwin developed a theory of evolution that is accepted by most scientists today.

Evolution by Natural Evolution

Darwin’s Theory of Evolution

• 1. Overpopulation- more offspring than can survive

• 2. Variation- individuals vary.• 3. survival of the fittest- best

adapted to survive. & natural selection- survivors pass on traits

• 4. When reproductive isolation occurs new species will form

Darwin’s TheoryWhat state do these represent?

Nature Selects• Adaptation is the process of becoming adapted to an

environment. It is an anatomical, physiological, or behavioral change that improves a population’s ability to survive.

Elephant Bird

http://www.pbs.org/wgbh/evolution/



Darwin’s TheorySurvival of Fittest

• A population is all of the individuals of a species living in the same area.

• Members of a large population compete for living space, food, and other resources.

• Only those that survive (best adapted) can reproduce and pass on their traits to the next generation.

• If you do not have traits that help you survive you go extinct and the traits are not passed on to the offspring

Darwin’s Theory

• Darwin’s ideas became known as the theory of evolution by natural selection.

• Natural selection means that organisms with traits best suited to their environment are more likely to survive and reproduce.

Whether a variation is helpful or harmful depends on the env

Mimicry- copies appearance of another org

Camouflage- blends

w/surroundings

Sphinx Moth

Flounders

Natural Selection

• Process in which something in a living thing’s surroundings determines if it will or will not survive to have offspring.

• Organisms suited to their env. Survive• Only the ones who survive can have offspring

and pass on traits

Summary of Darwin’s Theory

• Individuals in nature differ from one another

• Organisms in nature produce more offspring than can survive, and many of those who do not survive do not reproduce.

Summary of Darwin’s Theory

• Because more organisms are produce than can survive, each species must struggle for resources

• Each organism is unique, each has advantages and disadvantages in the struggle for existence

Evolution Summary

• Species alive today descended with modification from species that lived in the past

• All organisms on earth are united into a single family tree of life by common descent

Five Mechanisms of Microevolution

1. Genetic drift:Change in the gene pool of a small

population due to chance.

• Two examples:a. Bottleneck effectb. Founder effect

a. Bottleneck Effect

• Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size.

• Examples:1. Earthquakes2. Volcano’s

b. Founder Effect

• Genetic drift resulting from the colonization of a new location by a small number of individuals.

• Results in random change of the gene pool.

• Example:1. Islands (first Darwin finch)

The Speed of Evolution• Many scientists hypothesize that evolution occurs slowly, perhaps over

tens or hundreds of millions of years. • Other scientists hypothesize that evolution can occur quickly. • Most scientists agree that evidence supports both of these models.

• Tuatara is undergoing mutations faster than any other known species

Interpretations of Speciation

• Two theories:1. Gradualist Model (Neo-Darwinian):

Slow changes in species overtime.

2. Punctuated Equilibrium:Evolution occurs in spurts of relatively rapid change.

The Speed of Evolution• Many scientists hypothesize that evolution occurs slowly, perhaps over

tens or hundreds of millions of years. • Other scientists hypothesize that evolution can occur quickly. • Most scientists agree that evidence supports both of these models.

• Tuatara is undergoing mutations faster than any other known species

Gradualism• The model that

describes evolution as a slow, ongoing process by which one species changes to a new species

• According to the gradualism model, a continuing series of mutations and variations over time will result in a new species.

• A series of intermediate forms can indicate a gradual change from the earliest species to today’s species.

Gradualism• The model that

describes evolution as a slow, ongoing process by which one species changes to a new species

• According to the gradualism model, a continuing series of mutations and variations over time will result in a new species.

• A series of intermediate forms can indicate a gradual change from the earliest species to today’s species.

Darwins Theory Summary

• The most successful Individuals best suited for the environment survive and reproduce

• Species change over time

Punctuated Equilibrium Today

• Evolution by the punctuated equilibrium model can occur over a few thousand or million years, and sometimes even faster.

• For example, many bacteria have changed in a few decades.

• The antibiotic penicillin originally came from the fungus Penicillium.

• But many bacteria species that were once easily killed by penicillin no longer are harmed by it.

• Penicillin has been in use since 1943.

• Just four years later, in 1947, a species of bacteria that causes pneumonia and other infections already had developed resistance to the drug.

• By the 1990s, several disease-producing bacteria had become resistant to penicillin and many other antibiotics.

Allelic Frequency

• When the frequency of alleles is the same in all its generation, the population is in genetic equilibrium and is NOT evolving.

• If the allelic frequencies remain the same, phenotypes remain the same also.

Geographic isolation

• KAIBAB AND ABERT’S SQUIRRELOnce a single tassel-eared species, time and separation by the Grand Canyon has created two subspecies.

• Found only on the North Rim, the Kaibab Squirrel is endangered. Abert’s is found throughout the Four Corners area.

Geographic Isolation• Sometimes mountains,

lakes, or other geological features isolate a small number of individuals from the rest of a population. Over several generations, variations that do not exist in the larger population might begin to be more common in the isolated population.

• Also, gene mutations can occur that add variations to populations. Over time, the two populations can become so different that they no longer can breed with each other.

Evolve to different species

Geographic isolation

• same ancestors-different traits

• can cause speciation

• Grand Canyon squirrels

Adaptive radiation • pattern where

different species develop from a common ancestor to better fit their env.

• Ex. migration of camels

Adaptation• Traits that help living things

survive in their env.• Controlled by genes• How do traits help them

survive?

Adaptive Radiation

• Emergence of numerous species from a common ancestor introduced to new and diverse environments.

• Example:Darwin’s Finches

Species Variation

Caused by • Barriers• Different env• Traits change as

a result of natural selection

• Some organisms are separated by geographical boundaries and evolve into different species.

Evolution • Convergent E-• organism with

different ancestors become more alike because of adapting to their env.

• Divergent E. similar species become more distinct. (different)

Convergent Evolution• Species from different

evolutionary branches may come to resemble one another if they live in very similar environments.

• Example:1. Ostrich (Africa) and Emu (Australia).2. Sidewinder (Mojave Desert) andHorned Viper (Middle East Desert)

Coevolution• Evolutionary change, in which

one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species.

• Example:1. Acacia ants and acacia trees2. Humming birds and plants with flowers with long tubes

• Praying mantis & Orchid

Natural Selection

• Over time, natural selection results in changes in inherited characteristics of a population. These changes increase a species fitness in its environment

Examples of transitional fossils

Five Mechanisms of Microevolution

2. Gene Flow:The gain or loss of alleles from a

population by the movement of individuals or gametes.

• Immigration or emigration.

Modes of Action• Natural selection has three modes of action:

1. Stabilizing selection2. Directional selection3. Diversifying selection

Number ofIndividuals

Size of individualsSmall Large

1. Stabilizing Selection

• Acts upon extremes and favors the intermediate.



2. Directional Selection

• Favors variants of one extreme.



3. Diversifying Selection

• Favors variants of opposite extremes.



Speciation

• The evolution of new species.

• Darwin reasoned that the Galápagos finches must have had to compete for food.

Darwin’s ObservationsIdeas About Evolution

1

• Finches with beak shapes that allowed them to eat available food survived longer and produced more offspring than finches without those beak shapes.

• After many generations, these groups of finches became separate species.

Documents

Evidence of Evolution