Charles Darwin The Galapagos Islands greatly influencedbohshonorsbiology.weebly.com/uploads/8/4/7/6/84760492/2017_evolution... · 15.3 Darwin Presents His Case • Darwin mulled over

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15-1 The Puzzle of Life’s Diversity Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms. = Change over time

= Change in the frequency of

an allele in a population

Evolution is not

something that only happened in the past;

it is still going on. It does not happen to individuals, it happens

to populations.

The Galapagos Islands greatly

influenced Darwin’s ideas.

Observed: • Marine fossils atop mountains • Organisms have variations based upon

environment • Similarities between extinct fossils &

modern life • Organisms seem remarkably well suited

for their environment

Charles Darwin

Darwin found 13 species of finches on Galapagos Island. Each group of finches had its own niche (an organism’s habitat and its role in that habitat).

The shape of a tortoise’s shell corresponded to its habitat. • Tortoises on hot, dry islands had long necks and shells that curved

open around the neck and legs.

• On islands with rich vegetation, tortoise’s had a shorter neck and dome-shaped shell.

15-2 Ideas That Shaped Darwin’s Thinking Most people in Darwin’s day believed that Earth was only a few thousand years old, and that all of today’s species had existed unchanged since their creation.

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•Acquired Inheritance: Early theory where organisms could acquire and pass traits after birth

•Cause: environmental changes forced individuals to change

- organisms strive to improve themselves - unused body structures wasted away and most used structures develop

•Early Belief: Giraffes & Long Necks

–Long necks are result of stretching to reach leaves

–Extra length was passed on to offspring

•Problem: Traits acquired after fertilization cannot be passed to offspring

15.3 Darwin Presents His Case

• Darwin mulled over his ideas for 25 years before publishing

• Alfred Wallace sent Darwin an essay containing similar ideas; they presented their ideas together

• Darwin published his book 18 months later (1859)

The Theory of Natural Selection

Natural Variation • Defined: Inherited traits that make an individual different

from others

• Natural variation is found in all types of organisms.

• Much of this variation can be inherited

Artificial Selection

• Defined: Humans select (not naturally) traits thought to be advantageous

• Humans created diversity choosing specific traits to breed

–Dogs, Crops, Livestock

• Only inheritable traits can be passed down

• Importance: Shows life can change over a period of time

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Dog traits have been

selected by breeders for

centuries to produce

various breeds.

Plants have been

bred to produce

certain traits for

human use also!

•Four factors: 1) Overpopulation: more offspring are born than can survive

2) Variation: individuals of a population have differences 3) Adaptation: Some variations allow a better chance of survival

4) Descent w/ modification: Over time, those with advantages makeup more of the population

Not all these

wildebeest will

survive These kittens have

variations

The Myth

The Truth

- Natural selection

can act only on traits

that currently exist.

What is the beaver comic showing?

• Individuals don’t grow something

because they need it.

• Individuals don’t evolve.

Populations evolve!!!

Struggle for Survival

•High birth rates and limited resources cause competition

•Fitness: measure of the ability to survive & produce more offspring; fitness is a result of adaptation

•Adaptations can be physical, behavioral, or temporal

Adaptation

Defined:

An inherited trait that increases a population’s chances of survival and reproduction in a particular environment

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Adaptations Mimicry

Structural Adaptations

Behavioral Adaptation

Blue-footed boobies have a courtship display that is unique to their species; they will not mate until that courtship display is completed.

Temporal Adaptation Some cicadas reproduce every 13 years while others reproduce every 17 years, so the two groups never cross paths and reproduce.

Which rabbit is best adapted?

Do the dark rabbits turn white? No! They get

eaten.

What happens when environments change? Year 1 Background Year 10 Background

Those best adapted survive and reproduce.

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Changing Environments •As environments change…

–Those with adaptation: more likely to survive & reproduce

–Those without adaptation: more likely to perish

•Populations do not grow unchecked

–Limiting Factors: food, water, shelter, disease, predators

Summary of Darwin’s Theory of Evolution by Natural Selection

Overproduction Populations produce too

many young; many must die

Variation Individuals show variation; some

variations are more favorable

than others

Natural Selection Natural selection favors

the best suited at the time

Limited

Resources

Inheritance Variations are

inherited. The best

suited variants leave

more offspring.

Over time, natural selection results in changes in inherited characteristics of a population.

• Darwin’s principle states that over time, living species have descended, with changes, from other species.

• This implies that all living organisms are related to one another.

•Defined: Collection of every known fossil

•Most fossils found in sedimentary rock

•Age determined by depth

–new rock forms on top of older rock

•Evidence Conclusions:

1) Newer fossils are

more complex

2) Common ancestors:

relationships between

ancient & modern life

•AKA: Transition Fossils

–Archaeopteryx: shares both bird & reptile features

–Basilosaurus: shares whale & land mammal features

–Tiktaalik: shares fish & amphibian features

•Evidence Conclusion : Indicates common ancestry

Reptile Evidence

Teeth

Bony tail

Bird Evidence

Wishbone

Feathers

Whale Evidence

Long spine

Found in dried up

oceans

Land Evidence

Wolf-like teeth

Hind legs

Fish evidence

Scales

Fins

Found in dried-

up oceans

Amphibian evidence

Eyes on top of head

Wrist bones

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•Different

species show

similar

development

patterns

•Different body

plans become

noticeable

later in

development

•Evidence

Conclusion :

Indicates

common

ancestry

• Defined: similar body structures with very different functions

• Different environments lead to adaptations

– Ex: The forelimbs of animals

• Evidence Conclusion : Indicates common ancestry

• Defined: similar function with very different structures

• Analogous structures are not evidence of a common ancestor.

•Defined: Organs which have lost

most or all their original function

•Vestigial Human Parts:

–Gill slits = once used to breath

oxygen in water

–Yolk sac = once used to nourish

developing embryo

–Tailbone = once used for balance

–Appendix = once used to digest

plants

–Wisdom teeth = once used to

grind plant tissue

•Evidence Conclusion : Indicates

common ancestry

Human Embryo w/ Vestigial Structures Pythons have tiny femurs (leg bone)

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• DNA, RNA,

proteins

compared

• Genetic code

same for most

life

•More related species

have more similar

biochemistry

•Evidence

Conclusion:

Indicates common

ancestry

Ch. 16 Evolution of Populations

How Twitter is upgrading our gene pool…

16.1 Genes & Variation

•Gene Pool: All alleles within a population

•Relative Frequency: number of times that an allele occurs in a gene pool; usually expressed as a percent

Allele Frequencies: Sum = 100% Frequency of black allele =

Frequency of white allele =

Does gene frequency

equal phenotype frequency?

Why or why not?

No, because some black

mice carry the recessive allele.

12/20 = 60%

8/20 = 40%

White allele is recessive to black allele.

Sources of Genetic Variation

•Genetic variation can increase chances some survive changing environments

•Two main causes of genetic variation:

1. Mutations: Random changes to DNA sequence affect phenotypes; may affect fitness (ability to survive and reproduce)

2. Gene Shuffling: During meiosis, genes recombine in varying patterns; does NOT change the relative frequencies of alleles!

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16.2 Evolution as Genetic Change

Individuals that are better suited to their environment

(have high levels of fitness) survive & reproduce most successfully.

Natural Selection acts on phenotypes, not genotypes

• Happens over generations

• Can lead to changes in allele frequency (Evolution!)

Freq. of green allele:

Freq. of brown allele:

Directional Selection—Individuals at one end of the curve have a higher fitness than the rest.

Types of Selection

Disruptive Selection—Individuals at the upper and lower ends of the curve have a higher fitness; Selection creates two distinct phenotypes.

Types of Selection

Stabilizing Selection—Individuals near the center of the curve have higher fitness.

Types of Selection Genetic Drift

• Defined: Changes in allele frequencies due to chance –NOT natural selection

• Bottleneck effect

–Results in a loss of genetic variation (alleles)

–More likely in smaller populations

–Example: Natural disaster

•Pre-forest fire: Green is best adapted (blend better)

•Post-forest fire: Brown more likely to reproduce

–Survival UNRELATED to adaptations

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Genetic Drift: Founder Effect • Situation in which allele frequencies change as a

result of the migration of a small subgroup of a population.

• Example: Hawaiian fruit flies descended from 1 main type—very different from mainland fruit flies

Species •Defined: group of organisms that can interbreed and produce fertile offspring

–Different species rarely breed

–Interspecies breeding often

results in sterile offspring

•Ex: Horse x Donkey = Mule

•Ex: Lion x Tiger = Liger

–New species = when unable to successfully reproduce

16-3 The Process of Speciation

Defined: evolution of new species from an existing

species

• 5 factors that lead to evolution Natural Selection

Gene flow

Mutations

Sexual selection

Genetic drift

Speciation Gene Flow (Migration) •Defined: Movement of alleles from one population to another

- Increases variations in a

population

- Keeps differing populations similar

•If gene flow is prevented

- No variations (alleles) exchanged

- Populations are isolated

- Organisms adapt to their own

environment

- Can lead to speciation!

Reproductive Isolation •When populations are isolated for

a long time…gene flow stops

•When populations can no longer mate or no longer reproduce fertile offspring

•Final step in the development of a new species

1) Geographic Isolation:

o Organisms isolated by geographic barrier

Random DNA

mutations

Random DNA

mutations

Different

predators

Different

predators

Different

resources

Different

resources

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Reproductive Isolation •When populations are isolated for a

long time…gene flow stops

•When populations can no longer mate or no longer reproduce fertile offspring

•Final step in the development of a new species

1) Geographic Isolation:

o Organisms isolated by geographic barrier

2) Behavioral Isolation

o Organisms isolated by differing mating rituals

If the mating calls do not attract

each other, will they reproduce?

Is gene flow stopped?

Reproductive Isolation •When populations are isolated for a

long time…gene flow stops

•When populations can no longer mate or no longer reproduce fertile offspring

•Final step in the development of a new species

1) Geographic Isolation:

o Organisms isolated by geographic barrier

2) Behavioral Isolation

o Organisms isolated by differing mating rituals

3) Temporal Isolation

o Organisms isolated by differing times of reproduction

If one group mates during the spring…

And the other mates during the fall…

Is gene flow stopped?

•Constant creation of

chemicals for human use

is eliminating the “unfit”

organisms

–Ex: Antibiotics

eliminating unfit bacteria

Alexander

Fleming

discovered the

first

antibiotic…

penicillin

Current Evolution: •Constant creation of

chemicals for human use

is eliminating the “unfit”

organisms

–Ex: Antibiotics

eliminating unfit bacteria

Bacteria A

antibiotic

antibiotic

antibiotic

antibiotic

Bacteria B

antibiotic

antibiotic

antibiotic

antibiotic

Bacteria A has genes to create

enzymes that destroy the antibiotic Bacteria B does not have the genes to

make the enzymes to destroy the antibiotic

Bacteria A

Bacteria A is more likely to survive and _________________. REPRODUCE

When infected with a bacteria, we take

antibiotics.

The antibiotics are absorbed into the

bacteria.

•Constant creation of

chemicals for human use

is eliminating the “unfit”

organisms

–Ex: Antibiotics

eliminating unfit bacteria

–Ex: Pesticides

eliminating unfit pests

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•Constant creation of

chemicals for human use

is eliminating the “unfit”

organisms

–Ex: Antibiotics

eliminating unfit bacteria

–Ex: Pesticides

eliminating unfit pests

•Constant creation of

chemicals for human use

is eliminating the “unfit”

organisms

–Ex: Antibiotics

eliminating unfit bacteria

–Ex: Pesticides

eliminating unfit pests

Pesticides pesticides pesticides pesticides pesticides pesticides

Some “pests” are able to resist the

pesticides and survive. They will

reproduce with others who are

resistant. Over time, the entire

population is resistant.

•Constant creation of

chemicals for human use

is eliminating the “unfit”

organisms

–Ex: Antibiotics eliminating

unfit bacteria

–Ex: Pesticides eliminating

unfit pests

–Ex: Antivirals…

–Ex: Fungicides…

•This is natural selection!

–Allows resistant to

survive and reproduce

Read before the video, answer after…..

1. Why is the Russian prison system considered to be "ground zero" in the fight against TB?

2. What is responsible for the evolution of TB strains that are resistant to multiple drugs?

3. How does the misuse of antibiotics affect the evolution of disease-causing bacteria? Use the theory of natural selection to explain the growing resistance to antibiotics.

4. Why should we care about a resistant strain of TB in Russia?

Why Does Evolution Matter Now?