Chapter 15 Evolution

Think About It?

What is evolution?

Why does it happen?

How does it happen?

What is evolution?Change in a population over time at genetic level mutations

MutationsChange in DNA code can affect phenotype

REVIEW: From Gene to Protein

The Darwin Dude5 year voyage on Beagle (1831-36)

Naturalist: surveyed coast of S.A.

Wrote “Origin of Species”

Collected:–Rocks–Fossils–Plants–Animals

Charles Lyell’s Principles of Geology proposed Earth was millions of years old!

The Darwin Dude

Explained marine life at high elevation in the Andes

Giant fossil versions of smaller living mammals

Earthquakes could lift rocks great distances very quickly.

Lyell:

Galapagos Island Facts

Part of Ecuador

13 main volcanic islands

Formed between 5 - 10 MYA

Darwin & Galapagos Organisms adapted to their environment

“Darwin’s Finches”– Gould (ornithologist) finches were separate species not found any where else.

Mechanism for evolution = Natural Selection

Darwin believed new species appear gradually through small changes in ancestral species.

Breeders – can promote specific traits by selecting and breeding organisms that have the most exaggerated expressions of those traits.

Known as Artificial Selection!

Artificial Selection:

If humans could change species by artificial selection, the same process could work in nature!

Given enough time this process could produce new species!

Inference:

Artificial Selection:

Noteworthy Species

Darwin’s Finches

Adaptive Morpholog

y

Why do species change?

Variations & adaptations help organisms survive

Camouflage

Camouflage

Human population, if unchecked, would eventually outgrow its food supply, leading to a competitive struggle for existence.

Darwin believed Malthus’s ideas could be applied to the natural world.–Some competitors are better equipped for survival than others!

Thomas Malthus:

Natural SelectionOrganisms with favorable traits survive & reproduce

Variation is key

Natural Selection (cont.)

Struggle for existence

Species become better fit for their environment

If not they could DIE!

Natural Selection (cont.)

4 Main Principles (pg 421):

1. Variation2. Heritability3. Overproduction4. Reproductive

Advantage

Individuals in a population differ from one another.

Example:

1. Variation:

2. Heritability:Variations are inherited from

parents.

Example: X

3. Overproduction:

Populations produce more offspring than can survive.

Example: – 48 white tiger litters produces 148 cubs

–105 of them died without reproducing 71%

4. Reproductive Advantage:

Some variations allow the organism that possesses them to have more offspring than the organism that does not possess them.

Example: White tigers have powerful jaws & teeth, very strong sense of smell, sharp eyesight, and excellent swimmers!

Types of Natural Selection

1. Stabilizing Selection: Average phenotype favored

Ex. Human baby weight

Stabilizing Selection

Types of Natural Selection

2. Directional Selection: increases “extreme” versions of traits

Ex. Peppered Moth, Darwin’s finches

Peppered Moth: Natural

Selection

Directional Selection

Types of Natural Selection

3. Disruptive Selection: splits populations into 2 groups

Both extremes favored

Ex. Marine & Land Iguanas

Disruptive Selection

          

  

V = Variation: All life forms vary genetically within a population. It is this genetic variation upon which selection works.

          

  

I = Inheritance: Genetic traits are inherited from parents and are passed on to offspring.

          

  

S = Selection: Organisms with traits that are favorable to their survival get to live and pass on their genes to the next generation.

          

  

T = Time: Evolution takes time. Evolution can happen in a few generations, but major change, such as speciation, often takes long periods of time.

Evidence of Evolution

1.Fossil Record Fossils:

preserved evidence

Found in Sedimentary rock

Provides record of species that lived long ago.

Some similar to current ones!

Some species unchanged!

Evidence of Evolution

Similar fossil forms:

Glyptodon &

Armadillos

Species unchanged:

Horseshoe Crab!

Fossil Record (cont)

A. “Soft parts” don’t fossilize

B. Specific conditions are needed to form fossils

C. Hundreds of transitional fossils found

Classes of Traits:

Two major classes of traits while studying transitional fossils:–Derived traits: newly evolved features

–Ancestral traits: more primitive features that appear in ancestor forms.

2. Homologous Structures:

Anatomically similar structures

Evidence of common evolutionary origin

Evidence of Evolution

Homologous Structures

Analogous Structures:

Can be used for same purpose and can be superficially similar in construction but are not inherited from a common ancestor.

Analogous Structures:

3.Embryology: similarities in embryos

Evidence of Evolution

Embryology: Embryo – early, pre-birth stage of an organism’s development.

Vertebrate embryos exhibit homologous structures during certain phases of development.

4.Compararative Biochemistry: Organisms have similar DNA, genes and enzymes

Evidence of Evolution

Comparative Biochemistry:

The more closely related the species are, the greater number of amino acid sequences they will share.–Ex. Chimpanzees and Humans share 96% similar sequences!

Humans & Chimpanzees:

Human genome is 96% similar to great ape species.

Pan troglodytes (species of chimp) used in study – The number of genetic differences

between humans and chimps is ten times smaller than that between mice and rats.

Pan troglodytes (common Chimp)

5. Vestigial Structures: reduced in size, no longer have function

Evidence of Evolution

Formation of new species

Become genetically different

What is Speciation?

What are Species?Group of organisms that can interbreed & produce fertile offspring

Infertile SpeciesHorse + Donkey = Mule

64 ch. + 62 ch. = sterile

Liger

http://www.youtube.com/watch?v=WdTln4QwexQ&feature=related

Species Loop Hole Not a perfect definition

Used for classification

Some different species can produce fertile offspring

Grizzly Bear & Polar Bear

“Pizzly” or “Grolar”

Rate of Speciation Gradualism: Evolution occurring at slow rate

Punctuated Equilibrium: Evolution occurring at irregular rates

Cause of Speciation

1. Geographic Barriers

Mountains, Rivers, etc.

2. Environment Changes

3. Reproductive IsolationExamples:

–mating at different times

–birds mating with others who sing a particular song.

Cause of Speciation

1.Adaptive radiation (divergent evolution)

2.Coevolution3.Convergent

evolution

Patterns of Evolution:

Relatively short period of time

1 species gives rise to many

Usually occurs after mass extinctions

1. Adaptive Radiation:

Evolution of 1 species affects the evolution of another species.

2. Coevolution:

Unrelated species evolve similar traits

Under same environmental pressures

3. Convergent Evolution: