Unit 8 History of Biodiversity

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Misconception!

History of Biological DiversityEvolution: Charles Darwin’s travel

Charles Darwin

Developed the Modern Theory

of Evolution

Father of Evolution

Traveled around the world for 5

years on a ship called HMS

Beagle

Observed animals and plants

on the Galapagos Islands

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 Book

In 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 evolutionto mean cumulative change in a group of organisms through time.

• Natural selection is notsynonymous with evolution –it is a mechanism by which evolution occurs.

• Artificial selection (instead of nature) humans select which organisms get to reproduce and pass on genes.

Glyptodon(a CAR- sized mammal during the Ice Age, found in South America and related to today’s modern armadillo)

Armadillo(a cat sized mammal found in South America, Texas, Mexico & Florida)

An example of Evolution

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

6. Mechanisms of Natural Selection

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.

Lets use that fossil record…

1. Which of the following fossils (W, X or Y) is the youngest? Why?

W, it is closest to the top recent)

2. Which layer of earth is the oldest? Why?

Limestone, deepest layer

3. What layer might a paleontologist use to determine what caused a mass extinction?

Volcanic Ash, natural disaster

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)

Homologous

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

Examples of vestigial structuresWisdom teeth Tailbone

Appendix

Limb buds in snakes

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 DNAand protein sequences suggest relatedness.

Evidence of EvolutionCopyright © McGraw-Hill Education

5. Support for Evolution:

Geographic distribution

• The distribution of plants and

animals that Darwin studied 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).

6. Support for Evolution:Natural Selection

Genetic Variation in a population can lead to evolution!

What are some variations

you see in this

population of beetles?

Color, size, spots

Natural Selection

Genetic Variations (differences) in

the traits of a population will cause

individuals with “better” traits in an

environment leave more offspring

than other individuals.

“Survival of the fittest”= most babies

Practice!

What are the genetic variations of this mice population?

________________________

According to the definition given for fitness, which mouse would

biologists consider the fittest? ______________

Explain why this mouse would be the fittest.

_________________________________________

What adaptive trait do you think helped the ones who survived?

_______________________________________________

Color of fur Black Tan Tan and Black Cream

Age at death 2 months 8 months 4 months 2 months

Number of babies

produced by each female

0 11 3 0

Running speed 8 cm/sec. 6 cm/sec. 7 cm/sec. 5 cm/sec.

Tan

Reproduced to make the most offspring

Fur color camouflaged with the with sand, harder for predators to find

Color of fur, speed of mice

Natural Selection -

Genetic variation produces different adaptations.

Allows a population to become better suited

for their environment over time (Change over

time = evolution)

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.

Natural Selection

Ex: Bacteria can evolve into antibiotic

resistant strains (medicine will not kill the

bacteria). Good or bad for humans?

Types of 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 Natural 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

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.

http://twentytwowords.com/can-you-find-the-hidden-animals-in-these-20-wildlife-photos/

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

This “changing of the gene pool” (allele frequency) has a name

—› Evolution.

Evolution – the changes in the gene pool of a population over

time.

Speciation – formation of a new species

Reproductive Isolation

- 2 or more species cannot interbreed

1. Behavioral Isolation/Temporal Isolation

- occurs when 2 populations are capable of interbreeding

but have differences in courting rituals or breed at

different times.

Example: The eastern and

the western meadowlark

have overlapping ranges,

but they do not interbreed

because they have

different mating songs.

Ex . Rainbow trout spawn in the spring. Brook trout spawn in the fall.

These two species are isolated reproductively by time.

2. Geographic /Allopatric Isolation

- 2 populations are separated by geographic barriers

●examples: rivers, mountains, bodies of water

Common

ancestor

Lava-

geographical

barrier

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 gives rise to many species

More alike to less alike

Also known as adaptive radiation.

Examples: - Darwin’s Finches.

- Brown bears and polar bearsDraw this diagram in notes

Divergent or Convergent?

Coevolution Co-evolution occurs when, two or more organisms evolve

together.

Ex. Flowers and insects are good examples of this type of

coevolution. (mutualism)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.