Unit 11:Evolution & Natural SelectionBIOLOGY 10

Unit 11: EvolutionTable of Contents

Lesson 11.1: Camouflage & Mimicry

Lesson 11.2: Mutation & Adaptation

Lesson 11.3: Darwin’s Finches Lesson 11.4: Natural Selection Lesson 11.5: Evidence for

Evolution

Lesson 11.3: Charles Darwin

I can describe how Darwin came to describe natural selection while observing finches (birds) in the Galapagos Islands.

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A reconstruction of the HMS Beagle sailing off Patagonia.

Darwin’s Voyage of Discovery copyright cm

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5Voyage of the Beagle

Charles Darwin Born Feb. 12,

1809 Joined Crew of

HMS Beagle, 1831

Naturalist 5 Year Voyage

around world Avid Collector of

Flora & Fauna Astounded By

Variety of Life

copyright cmassengale

6Darwin Left England in 1831

Darwin returned 5 years later in 1836

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The Galapagos IslandsSmall Group of Islands 1000 km

West of South AmericaVery Different ClimatesAnimals On Islands Unique

TortoisesIguanasFinches

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The Galapagos Islands Finches on the islands

resembled a mainland finch

More types of finches appeared on the islands where there was a variety of available food (seeds, nuts, berries, insects…)

Finches had different types of beaks adapted to their type of food gathering

Darwin’s Finches

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Distribution of Food on The Galapagos Islands

Predicted Finch Distribution Predict the distribution (presence or absence) of each type of

finch on each of the various Galapagos Islands. Fill in the table on your handout. HINT: Compare the preferred food type & beak shape of each

bird with the type of food available on each island.

Actual Finch Distribution

What if . . . The seeds on Espanola started to increase in size?1. What would you expect to happen

immediately to the population of Small Ground Finches?

2. What would you expect to see happen to the population over the next 20 years?

3. What would happen if the size of the seeds decreased again in the future?

Darwin’s Conclusions The environment

determined which animals would survive and which would die off.

Those adapted to the new environment survived and became different from their mainland relatives.

Examples: Iguanas & Finches

Lesson 11.4: Natural Selection

I can describe how variation can provide populations an advantage for survival

I can identify examples of adaptations that may have resulted from variations favored by natural selection.

Natural Selection

Natural Selection: Organisms that are better adapted to an environment survive and reproduce more than others.

Natural Selection

The Theory of Natural Selection is based on four concepts:1. Overproduction2. Variation3. Competition4. Selection

1. Overproduction

Each species produces more offspring that can survive

2. Variation

Each individual has a unique combination of inherited traits.

Adaptation: an inherited trait can increase an organism’s chances of survival

What adaptations do you see?

What adaptations do you see?

Why is Variation Important? Because the environment

changes. The more variation within a

species, the more likely it will survive. EX: A deadly disease strikes an

area, and only those who are immune survive.

The more variation of types of species in an habitat, the more likely at least some will survive. EX: Dinosaurs replaced by

mammals

Which community has a better chance of surviving a natural disaster?Community A Community B

3. Competition

Individuals COMPETE for limited resources: Food, water, space, mates, etc.

Natural selection occurs through “Survival of the fittest” Fitness: the ability to survive and

reproduce Best adapted to the environment

Not all individuals survive to adulthood

4. Selection The individuals with the best traits /

adaptations will survive and have the opportunity to pass on it’s traits to offspring. Natural selection acts on the phenotype

(physical appearance), not the genotype (genetic makeup)

Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

4. Selection

Individuals with traits that are not well adapted to their environment either die or leave few offspring.

Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals that carried them.

Q: WHO selects the traits for wild plants and animals?

INDIVIDUALS THAT HAVE TRAITS THAT ARE BEST ADAPTED FOR THE CURRENT ENVIRONMENT ARE THE ONES THAT SURVIVE TO BREED AND PASS ON THEIR

GENES TO THE NEXT GENERATION.

NOBODY!!

Organisms that do not have the beneficial traits either die or don’t have as many offspring.

There is no agent involved in natural selection.

Natural selection is a process of elimination

Natural Selection is Survival of the Fittest

“Survival of the Fittest”● Evolutionary fitness isn’t a measure of physical

fitness but of reproductive fitness.● Fitness- Ability to survive and produce

offspring in an environment

What acts as a selection pressure on a population?• Competition for food• Competition for a mate• Changes in the environment• Predators• Parasites• Human-caused changes to the environment

(deforestation, climate change, pollution, etc.)

Sexual DimorphismSexual Dimorphism: Differences

between individuals of different sex of the same species

Male is larger in most mammalsIn insects, spiders, birds, reptiles,

amphibians the female is usually larger

In almost every species except for humans, the male is more colorful, as it is his job to attract a mate.

Sexual Dimorphism

Female Male

Sexual Dimorphism - Males

Sexual Dimorphism - Females

Sexual Selection Sexual selection: selection

towards male/female characteristics that leads to sexual dimorphism

How does this happen?Female mate choiceMale-Male competition

Sexual Selection – The Bower Bird

Remember that natural selection does not grant

organisms what they “need,” it only works

with what they are “born” with…

This is the perfect tool for

the job!

FACTORS AFFECTING NATURAL SELECTION:

Overproduction: the more offspring born, the more mouths to feed which equals fewer resources available to all

Variation: if there is no variation within species, all individuals will have the same traits and an equal chance of surviving and reproducing

FACTORS AFFECTING NATURAL SELECTION:

Competition: different species compete or fight over resources which can affect the number of organisms that survive from generation to generation

Environmental change: changes in the environment may favor certain characteristics over others – ex. Having thick fur during a particularly cold winter may favor an organism’s survival

Lesson 10.4: Evidence for Evolution

I can give several examples of evidence supporting the theory of evolution.

Evolution

Evolution = change in populations over time.

More specifically, evolution is genetic change in populations, often leading to observable changes, over time.

EvolutionSeveral key points:

1. Evolutionary change does not happen overnight.

2. Changes must be heritable – able to be passed on from one generation to the next.

Evidence for Evolution:

Fossil Record Homologous Body Structures Vestigial Organs Embryology Biochemical Evidence (DNA)

The Fossil Record Fossils: the impression in the earth

left by the remains of dead organisms.

Fossil Record: a record of the history of life on Earth, documented by fossils.

Archaeopteryx Similarities between

different fossil species and between fossil species and modern species illustrate a relationship

Missing link between reptiles and birds

Geological and fossil evidence show that the Earth has evolved (changed over time) too.

Homologous Body Structures

Homologous Body Structures: similar anatomy in different types of animals because of common ancestor

Analogous Body Structures Analogous Body Structures: similar

anatomy in different types of animals because similar environmental pressures, NOT an ancestral relationship.

Vestigial Organs Vestigial Organs: “leftover”

traces of evolution that serve no purpose now.

Embryology Embryology: embryos of all

vertebrates are very similar early in their development.

Biochemical Evidence Biochemistry: DNA with more

similar sequences suggest species are more closely related EX: Humans and

chimpanzees share more than 98% of identical DNA sequences

Review Questions

1. Define "Evolution" & "Natural Selection". 2. Describe the 4 steps of Natural Selection,

giving an example of each. 3. Explain the importance of "Variation". 4. Does Natural Selection act on an

organism phenotype or genotype? Explain! 5. List the 5 evidences that support the

Theory of Evolution.