evolution. intro to evolution and darwin’s theory

Evolution

Intro to Evolution and Darwin’s Theory

Peppered Moths of Industrial England

Evolution: Change over time

Why should we study evolution?-Scientist use evolution to study

biology.-It helps us understand

relationships between species in ecosystems.

-It explains the development of antibiotics resistance and insecticide resistance.

-Understanding relationships between organisms can help us make conclusions in medical research. It explains how HIV and influenza can change (mutate).

Darwin’s Theory: Darwin combines his evidence and

develops his theory of evolution.

Change via Natural Selection.1. All species have natural genetic variation as a result of

random mutation.Variation: Genetic diversity, changes within a

speciesWhat causes variation within a species?

a. Mutation: DNA change during replicationb. Crossing Over:

SummaryTwo moths that belong to the same species but are different colors is an example of what?

The difference in color was caused by a change in the DNA of the moth species. What do we call a change in DNA?

Variation

A Mutation

Darwin’s Theory: Darwin combines his evidence and develops his

theory of evolution.

2. Organisms produce more offspring than can survive, and the environment presents many challenges (selective pressures) to survival.

Example: Predator-prey interactions, resource shortage, changes in environmental conditions.

3. There is a struggle for survival. Struggle= Competition. The fittest individuals will be able to survive (those whose genes give them an advantage.)

Question: Are the fittest individuals the same in all environments?

No, in different environments, different traits will be advantageous.

Darwin’s Theory: Darwin combines his evidence and develops his

theory of evolution.

4. Traits from the survivors are passed on to the offspring. The frequency of the survivors’ traits increase in the population over time as the population adapts to its environment.

Adaptation: Any variation that allows an organism to survive and reproduce successfully.

Examples: Resistance to toxins, camouflage, ability to conserve water, antibiotic resistance.

Darwin’s Theory: Darwin combines his evidence and

develops his theory of evolution.

5. Individuals (and Species) that are not able to survive and reproduce will become more susceptible to die off (become extinct). Their traits/genes will become extinct with them.

Susceptible= Likely to be affected

Summary

What were the variations in the “organisms” in the moth slides?

What was the selective pressure?

Was the selective pressure from a predator or prey?

Could little variation in a species cause an organism to die off (become extinct)? Why or why not?

Light versus dark moths

Birds

Predator

Yes, if there is a little variation within a species; they may not be able to adapt well to any changes in their environment.

Genetics and Natural Selection

Natural selection changes the frequency of certain genes within a population over time as the population adapts to its environment.

**Evolution works at the POPULATION level- NOT the individual level**

Gene Pool- The entire collection of genes among a population.

Genetics and Natural Selection

Remember that there can be different versions of a gene. Each version of a gene is called an allele. You inherit one allele from each gene from each parent.

Allelic Frequency: The % of a particular allele within a gene pool can increase or decrease.

If an organism survives in their environment they are able to reproduce and pass on their genes to their offspring. This will increase their alleles in the population.

Summary

In certain cattle, red hair (R) is dominant to white hair (r). Heterozygous (Rr) cattle are roan in color and have both red and white hair. What would happen to the (r) allele if the white calves were more easily noticed by coyotes?The percentage of the r allele would decrease in the population. Therefore, the frequency of white or roan calves being born would decrease.

Behavior

Behavior

Behavior: How an organism reacts to changes in its internal and external environment.

What is the affect of natural selection on behavior? Behaviors will be maintained or removed based on their overall contribution to the Fitness of an individual. The behavior must be genetic because selection changes the frequency of that gene (alleles) in the gene pool.

Example: Read the passage below and answer the questions that follow.

1. What question was Tinbergen attempting to answer with his experiment?

2. Why did Tinbergen set up one area with camouflaged eggs and no shell fragments?

3. Explain how you would interpret the behavior of the gulls based on this experiment.

4. How is the behavior of the gulls linked to natural selection?

Was the removal of shell fragments advantageous to the Black-headed Gulls?

To have a control group

The Gulls remove the fragments to protect the whole eggs from being eaten by the Carrion crows.

The gulls that removed the egg fragments had a greater probability that their offspring would survive, and, therefore, this behavior was selected for.

Speciation

Speciation

Speciation: The evolution of a new species from old species.

How can you tell members of 2 different species apart? By physical characteristics, DNA, and behavior.

What is a species? A group of organisms that can mate and produce fertile offspring.

Speciation

How can natural selection produce a new species?1.Natural selection causes changes in

allelic frequency of a population.2.Different parts of a population might

change in different ways.3.Due to these changes, the 2 parts of the

population are now unable to mate.

Speciation

Reproductive Barrier: Any factor that keeps fertile offspring from being produced.

4. If the 2 parts can no longer mate, this means a new species has evolved.

The evolution of a new species from old ones is called speciation.

Speciation

Examples of Reproductive Barriers:

Geographical Barriers: Rivers, Mountains, canyons

Temporal (Time) Barriers: Species do not mate at the same time.

Summary

Consider the species shown in graphs above. If the population of small (1cm) mosquitoes experiences a mutation that causes them to become unable to mate with those that are larger (2.5cm), which of the following would most likely occur over time?

a. The small mosquitoes could become a separate species from the larger mosquitoes.

b. The small mosquitoes could mate with the larger mosquitoes forming more mid-sized mosquitoes.

c. The population would return to one more like that found during 1990.

Evidence of Evolution


1.Physiological Adaptations: Changes in organism’s metabolic processes.Examples: Bacteria developing antibiotic

resistance.2. Fossils: Any evidence of an organism that

lived long ago.Most fossils form in sedimentary rock. This type of rock is formed when sediments(sand, pieces of rock) form layers and is compressed together. Organic matter trapped between layers decays slowly and a fossil is left behind.

Examples

Footprints Pieces of bone


How do fossils show evidence of evolution? They can show us what organisms looked like in the past, and we can trace how they change over time.

3. Biochemistry: Nearly all organisms share DNA, ATP, and many enzymes among their biochemical molecules. The more closely related organisms are, the more similar their DNA (and therefore, amino acids) will be.


The enzyme cytochrome c, occurs in organisms as diverse as bacteria and bison. Biologist compared the differences that exist among species in the amino acid sequence of cytochrome c. Organisms that are biochemically similar have fewer differences in their amino acid sequence.

SummaryThe diagram to the right represents different layers of soil. The letters represent fossils of three different species of organisms.

Which species is most likely oldest?

Which species most likely existed at the same time?

C

A&B and A&C


Homologous Structures: Structures found in organisms with a common evolutionary history.

Examples: Bat wings, whale fins, and human arms all have similar bone structure and are all mammals.

How do homologous structures show evidence of evolution? If two organisms have homologous structures they are related and have come from a common ancestor.


5.Vestigial Structures: Structures that have a reduced (or no) use in an organism, but might have had a larger use in an ancestral species.

Examples: Human tail bone, whale pelvis bone,

snake “leg” bones.

How do vestigial structures show evidence of evolution? They indicate a structural history.


Embryology: The study of an organism’s early development.

How does embryology show evidence of evolution? Organisms who share embryological similarities are probably related (Share a common ancestor).

Summary

Name six types of evidence used to determine evolution in organisms.

1.Physiological Adaptations2.Fossils3.Biochemistry4.Homologous Structures5.Vestigial Structures6.Embryology


Diversity: The number of different species in an ecosystem.Why is a more diverse ecosystem more stable? There is more than one organism to fill a role, so if one dies, there is a “back up.”

Example: An ecosystem with one producer will fall apart, if that species goes extinct.

How can natural selection increase diversity? Natural selection provided a way for new species to evolve, which can increase diversity.


Phylogeny: an organism’s evolutionary historyAn organism’s phylogeny can be diagram using a phylogenetic tree. A phylogenetic tree is a branching diagram that shows evolutionary relationships.

How is the phylogeny of an organism determined?Scientist classify organisms based on their similarities in DNA, anatomy, and behavior.

Common Ancestor: A species from which two or more species separated from.

Summary

Many species are threatened with extinction. How will this affect biological diversity?

Phylogenetic Tree

Example #1 Example #2

Questions

1.Which organism is most closely related to a flowering plant?

2.Which organism is the most primitive?

3.What kingdom is the common ancestor of all these plants?

FERN

Protista

Protista

Example #3

Summary

1.What animal is most closely related to a bird?

2.What animal is most closely related to a lizard?

3.Is a mammal more closely related to a turtle or a shark?

4.Is a shark more closely related to an amphibian or a turtle?

5.Is a crocodile more closely related to a lizard or a turtle?

Crocodile

Snake

Turtle

amphibian

Lizard

evolution. intro to evolution and darwin’s theory

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