Ch. 14 Evolution

Evolution : • the process of change that produces new

species from already existing species.• Change in a species due to mutation of the

DNA code that occurs over a long time.

evolution: generation-to-generation change in theproportion of different inherited genes in a population that account for all of the changes that have transformed life over an immense time.

Species – group of closely related organisms that can mate and produce fertile offspring.

Adaptation: inherited characteristicthat improves an organism's abilityto survive and reproduce in a particular environment.

Evolution of Air Breathing:

Evolution of Brains:

Early Ideas about Evolution

Originally people thought that the species on Earth were permanent – the same species had always been here.They also thought that the Earth wasn’t that old – lessthan 10,000 years old.

In the 1700’s, people began to find fossils.

The discovery of fossils meant the Earth might be much older than thought.

It was also noted that the fossils were different fromknown living creatures, and that different living specieswere often similar to each other while not being exactly the same.

Lamark’s early theory of evolution

Lamark had the idea that specieschange over time.

Evolution involvesadaptations

Lamark’s Theory

•Species adapt because of what they need or want.•Use of structure results in evolution –

called “acquired characteristics”.•acquired characteristics are passed on

to next generation.

Lamark’s theory is no longer accepted, but he was the first to suggest that evolution occurs and that it is related to adaptations.

Darwin’s Theory of Evolution

1859 - Charles Darwin publishes The Origin of Species.

Darwin’s Voyage on “Beagle” shaped many ideas of Biology

Purpose of voyage – Sail around world & survey little known coastal areas

HMS Beagle Voyage 1835

Charles Darwin

Natural Selection:“Survival of fittest”Competition for resourcesBest adapted species surviveThe Fittest reproduce

natural selection: process by which individuals with inheritedcharacteristics well-suited to theenvironment leave more offspringthan do other individuals

Darwin’s key ideas:

• A. REPRODUCTION: Organisms produce more offspring than can survive

• B. VARIATION:Variety in traits exist• C. SURVIVAL OF THE FIT: Some traits

allow survival & are passed on• D. Over time certain variations make up

most of a population & they may be different from their ancestors

Evolution Evidence:

1. Adaptations2. Fossils3. Comparative anatomy4. Comparative embryology5. Comparative Biochemistry6. Plate Techtonics

1. Adaptations: features suited to a particular environment that allow organisms to survive.

Inuit people, who live in the extreme cold of the Arctic, have short, stout bodies that conserve heat.

Masai, people,who live in the arid lands of eastern Africa, have tall, lean bodies that disperse heat well.

Plant Adaptations:Venus Fly Trap• Captures

Animals• Acquires

Minerals• For Photo- synthesis

Help!!!

Leaf Adaptations:

Succulents

• Thick

• Store Water

• Prevent Drying out

Leaf Adapatations:

Pine Needles• Shed snow• Less water

loss• Reduced

surface area• Tolerate wind

2. Fossil Evidence:

• Once living remains of organisms

• Limited:1. Type of material

preserved (bone, shell, impressions, amber)

2. Incomplete record

3. Easily disrupted

Plant Fossil:

3. Comparative Anatomy: Structural similarities link related species

Comparative Anatomy Structures:

Analogous:

1. Different ancestors

2. “analogy”=like

3. Different underlying structures

4. Same Function

5. Similar Environments

Homologous:

1. Same ancestor

2. “homo”=same

3. Same underlying structures

4. Different Functions

5. Different Environments

Analogous Structures• Different underlying structures (different ancestors)

• Same function, similar environments

Fly wing

Bird Wing

Homologous Structures: Same underlying structures, different functions,

different environments & common ancestor

Bird Wing

Porpoise Flipper

4. Comparative embryology:Similar embryo development in closely related species

5.Comparative Biochemistry• Similar DNA

sequences=• Similar Gene

segments of the DNA

• Code for similar traits

• In closely related species

6. Plate Techtonics

• Geological theory:• Continental masses were one

land mass that explains• Closely related species have

common ancestors on now separated continents

14.3

population: group of individuals of the same species living in a particular area at the same time.

Over time, the isolated populations would becomemore and more different.

In the Galapagos islands, an original species offinch eventually spread out to the separate islands.

variation: difference among members of a species

And over many generations, the populations couldbecome different enough to be separate species.

artificial selection: selective breeding of domesticated plantsand animals to produce offspring with desired genetic traits.

Sometimes artificial selection occurs when we don’twant it to.

Examples of this include:•insect populations that become resistant to pesticides•germs that become resistant to antibiotics

Artificial selection supports the idea that evolution could have created different species.

14.4 Microevolution – genetics and natural selection.

gene pool: all of the alleles in all the individuals that make up a population.

microevolution: evolution on the smallest scale –the generation-to-generation change in the frequencies of alleles within a population

Gene pool

• Group of reproducing organisms

• Specific frequency of allele types:

25% AA

50% Aa

25% aa

Changes in the Gene Pool:

• New mix of allele frequencies:

10% aa

60% Aa

30% AA

Hardy-Weinberg equilibrium: condition that occurs when the frequency of alleles in a particular gene pool remain constant over time .

When the frequency of alleles does not change, evolution is not occurring.

Usually though, the allele frequencies change over time. This is called genetic drift.

genetic drift: change in the gene pool of a population due to chance.

Genetic drift results from random mating and the randomness of meiosis in producing the genes ineggs and sperm.

Genetic drift has the greatest effect on small populations.

The Bottleneck effect – when a natural disaster greatly reduces the size of a population. This can greatly change the allele frequencies.

The Founder effect – when a few members of a population colonize a new area, genetic drift maygreatly increase in the new area.

Two special examples of genetic drift:

Genetic drift and natural selection change thegene pool’s frequency of alleles the most.

Other processes that change the gene pool are:

gene flow: exchange of genes between populations.

mutations: changes in an organisms DNA. If mutations occur in gametes, they may introducenew genes into the population.