Unit 10: History of Biological DiverPAP Evolution: Darwin’s travel

Darwin’s Theory of Evolution by Natural SelectionCopyright © McGraw-Hill Education

Developing the Theory of Evolution

The Galápagos Islands• Darwin noticed that the

different islands all seemed to have their own, slightly different varieties of animals.

• Somewhat similar species that suited their particular environment.

Origin of Species: Darwin’s BookIn 1859 On the Origin of Species presented evidence and proposed a

mechanism for evolution that he called natural selection.

Darwin’s Theory of Evolution by Natural SelectionCopyright © McGraw-Hill Education

• Today, scientists use evolution to mean cumulative change in a group of organisms through time.

• Natural selection is not synonymous with evolution – it is a mechanism by which evolution occurs.

Peppered Moth: Natural Selection• The light colored form was the predominant form in England prior to

the Industrial Revolution.• Around the middle of the 19th century the darker form began to appear.

It was first reported in 1848. By 1895 98% of the moths in Manchester were the dark variety.

• In recent years, the burning of cleaner fuels and Clean Air regulations has reduced the pollution there and the lighter colored moths have increased in numbers.

• https://www.youtube.com/watch?v=aTftyFboC_M

Natural Selection: a. Artificial Selection – humans select for variations

in plants and animals that they find useful. b. Natural Selection

– also means “Survival of the Fittest”.

- Fitness in this sense does not mean strongest.

- Fitness in Darwin terms means reproduction. The one who survives long enough to reproduce the most is the one with the highest fitness.

Types of Selection -Evolution acts on the phenotype of the individual, not the

genotype. - There are 4 types of selection that can occur on a

population. 1. Directional Selection – when individuals at one end of the curve have a higher fitness than

individuals in the middle or at the other end of the curve.

2. Stabilizing Selection – when individuals near the center of the curve have higher

fitness than individuals at either end of the curve, narrowing of the graph.

3. Disruptive Selection– when individuals at either end have a higher fitness and

individual near the middle of the curve are selected against.

- Over time with enough selection a population can go through genetic drift.

a. genetic drift – random change in allele frequency.

4. Sexual Selection: the ability to attract a mate

Worksheet

Evidence of EvolutionCopyright © McGraw-Hill Education

Support for Evolution• Evidence for evolution comes from:

1. The fossil record: remains in layers of rock

2. Comparative anatomy

a. Analogous structures

b. Homologous Structures

c. Vestigial Structures

3. Comparative embryology:

4. Comparative biochemistry

5. Geographic distribution

1. Support of Evolution: Fossil Record

• Fossil Record – Fossils are the remains of ancient organisms found in layers of rock in the Earth.

Support of Evolution• The layers of rock

tell the history of the Earth, while the fossils found within the rock tell a history of life.

• The fossils are thought to be the same age as the rock they are found in.

Evidence of EvolutionCopyright © McGraw-Hill Education

Support for Evolution: The fossil Record• Researchers consider two major classes of traits

when studying transitional fossils:

• Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors.

• Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms.

Evidence of EvolutionCopyright © McGraw-Hill Education

2. Support for Evolution: Comparative Anatomy

• A. Homologous structures are anatomically similar structures inherited from a common ancestor.

• Similar structures with different function (similar bones) (common ancestor)

Evidence of EvolutionCopyright © McGraw-Hill Education

Support for Evolution

Comparative anatomy

• B. Analogous structures can be used for the same purpose and be superficially similar in construction, but are not inherited from a common ancestor.

• Structures are different but have similar function

Evidence of EvolutionCopyright © McGraw-Hill Education

Support for Evolution

Comparative anatomy

• C. Vestigial structures are structures that are the reduced forms of functional structures in other organisms.

• Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost.

snake pelvis human appendix

3. Support for Evolution: Comparative embryology

• Embryos of many animals with back-bones are very similar.

Evidence of EvolutionCopyright © McGraw-Hill Education

4. Support for Evolution: Comparative Biochemistry• Common ancestry can be seen in the complex metabolic molecules

that many different organisms share.

• The more closely related species are to each other, the greater the biochemical similarity.

Similarities in DNA and protein sequences suggest relatedness.

Evidence of EvolutionCopyright © McGraw-Hill Education

5. Support for Evolution: Geographic distribution

• The distribution of plants and animals that Darwin were what first suggested evolution to him.

• The distribution of plants and animals around the world is studied in the field of biogeography.

• Evolution is linked to migration patterns, climate, and geological forces (such as plate tectonics).

Activity

Evidence of EvolutionCopyright © McGraw-Hill Education

Adaptation- an inherited trait that increases a population’s chance of survival and reproduction in a particular environment

• Fitness is a measure of the relative contribution an individual trait makes to the next generation.

• The better an organism is adapted to its environment, the greater its chances of survival and reproductive success.

•Through adaptations, populations often become suited to a specific job called a niche.

• 1. niche – the role a population plays in a habitat

- job, profession, role• 2. Competition arises when 2 populations

occupy the same niche.

Evidence of EvolutionCopyright © McGraw-Hill Education

Adaptation

Types of adaptations

• Camouflage is a suite of morphological adaptations that allow an organism to blend into its environment.

• Mimicry is a type of morphological adaptation where a species evolves to resemble another species.

• Antimicrobial resistance develops in some bacteria in response to sub-lethal exposure to antibiotics.

Camouflage

Mimicry

Population Genetics - study of the traits in a population

A. Population – a group of interbreeding organisms (a species) living in a given area

B. Gene Pool – combined genetic material of all the members of a population

C. Gene Flow-the transfer of allele or genes from one population to another

D. Genetic Drift- any change in the allelic frequency in a population that results from chance

E. Allele – forms that a gene can take

F. Allele Frequency – the number of each allele for a trait

2. This “changing of the gene pool” (allele frequency) has a name —› Evolution.

3. Evolution – the changes in the gene pool of a population over time.

Speciation – formation of a new species Reproductive Isolation

- 2 or more species can not interbreed

Prezygotic: Its happens before fertilization: different reproductive times and different mating songs.

Postzygotic: Its happens after fertilization: fertilization has occurred but results in sterile offspring (Mule)

Horse 60 chromosomes--------gametes 30

Donkey 62 Chromsomes--------gametes 31

1. Behavioral Isolation

- occurs when 2 populations are capable of interbreeding but have differences in courting rituals or breed at different times

2. Geographic /Allopatric Isolation

- 2 populations are separated by geographic barriers

●examples: rivers, mountains, bodies of water

Types of Evolution

Convergent Evolution: less alike to more alike Divergent Evolution=Adaptive Radiation: more alike to

less alike Coevolution: evolve together Punctuated equilibrium: happens in short period of time

Convergent Evolution: Occurs when different organisms that live in similar environments become

more alike in appearance and behavior. Less alike to more alike Examples: - Bird wings/insect wings

- Shark fins/dolphin fins

Draw the diagram in Notes

Divergent Evolution=Adaptive Radiation One species give rise to many species More alike to less alike Also known as adaptive radiation. Examples: - Darwin’s Finches.

- Brown bears and polar bears

Draw this diagram in notes

Punctuated equilibrium predicts that a lot of evolutionary

change takes place in short periods of time tied to speciation events.

Gradual equilibrium Predicts that little of evolutionary

change takes place in small gradual steps