EVOLUTION: PROCESSES & PATTERNS

EVOLUTION:PROCESSES & PATTERNS

BIOLOGY EOC BENCHMARK

SC.912.L.15.13 Describe the conditions required for natural selection, including: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success.

VIDEO: Simpson Evolution

Why is Homer evolving?

Convergent EvolutionConvergent Evolution

different organisms that live in similar environments become more alike in appearance and behavior.

environment selects similar adaptations in unrelated species.

Organisms develop analogous structures (same function, but different origins)

different organisms that live in similar environments become more alike in appearance and behavior.

environment selects similar adaptations in unrelated species.

Organisms develop analogous structures (same function, but different origins)

CoevolutionCoevolution

two species evolve together. There is a mutual evolutionary influence

between two species. The species have a symbiotic relationship

(interaction between members of two populations).

Example: - Birds and flowers

two species evolve together. There is a mutual evolutionary influence

between two species. The species have a symbiotic relationship

(interaction between members of two populations).

Example: - Birds and flowers

Divergent EvolutionDivergent Evolution ancestral species gives rise

to a number of new species that are adapted to different environmental conditions and are less alike.

Often occurs when a species colonizes a new environment.

Also known as adaptive radiation.

ancestral species gives rise to a number of new species that are adapted to different environmental conditions and are less alike.

Often occurs when a species colonizes a new environment.

Also known as adaptive radiation.

THE EVOLUTIONS OF POPULATIONS

THERE ARE FOUR MECHANISMS THAT CAN GIVE RISE TO EVOLUTION:1.MUTATION 2.GENETIC DRIFT 3.MIGRATION (Gene Flow) 4.NATURAL SELECTION

Greatly and quickly seen in isolated populations like those on islands. - Allele frequency will change over generations; situations/ENV will favor one allele over another- Those populations at equilibrium are not evolving- Species with more genetic diversity will adapt better to environmental changes

GENETICS OF WHITE BENGAL TIGERSIn nature, White Bengal tigers arises from the mating of two Bengal tigers with recessive genes for the white color of fur. The gene is recessive has the effect that offspring (cubs / kittens) only become white if they inherit the recessive gene from both parents.It is the same principle as with brown and blue eyes. The inbreeding producing all these White tigers is neither good nor healthy for the tigers. In nature White tigers have, at least theoretically as there probably arent any, a less chance of surviving than normal colored tigers due to their lack of camouflage compared to the normal Yellow Tigers.

Below is a very simplified illustration (Fig 1) of how the transfer of genes coding for fur color works. Consider to yellow Bengal Tigers mating. If they are both carriers of the recessive gene there's a 25 percent chance that their cubs will be white. If a white and a yellow Bengal tiger mates there's a 50 percent chance that the offspring will be white. The chances of getting more White tigers can be enhanced by letting tigers that are related mate. This is however the definition of inbreeding.

TIGER POPULATION

THE EVOLUTIONS OF POPULATIONS

Proportion of orange fur-pigment alleles in the population

Proportion of white fur-pigment alleles in the population

Allele frequencies:

Evolution is a change in the allele frequencies of a population over time. For example, a change in the proportion of pigment alleles in the population of tigers means that evolution has occurred.

Normalphenotype

MUTATIONA mutation can createa new allele in an individual. When this happens, the population experiences a change in its allele frequencies and, consequently, experiences evolution.

MECHANISMSOF

EVOLUTION

EVOLUTIONARY CHANGE: MUTATION

Despite mutation’s vital role in the generation of variation, mutations almost always cause early death or lower the reproductive success of an organism.

DNA

Mutagen

Mutated protein

Mutatedphenotype

Mutated base-pair sequence

Normal base-pair sequence

Normal protein

#1

Mutations• Are rare because you have

self correcting enzymes• Natural Process that

produces genetic diversity• Not all mutations are bad

– Some won’t affect the body at all

• Blood types/ear lobes

– Some are advantageous

(thumb)

Brain Pop: Genetic Mutations

COMPUTER ACTIVITY: Sex and the Single Guppy

The purpose of this activity is to analyze how guppy populations change over time. The simulation activity allows you to start with a pool of guppies and your choice of predators, you will be able to watch what happens to your guppy population and how the introduction of predators can affect the guppy's appearance. The simulation will help you understand what pressures drive guppy evolution.

POPULATION BEFOREGENETIC DRIFTAllele frequencies:

MECHANISM FOR EVOLUTION - GENETIC DRIFTpopulation can experience random changes in allele frequency that do not

influence reproductive success which leads to evolution

FIXATIONGenetic drift leads to fixation when an allele’s frequency becomes 100% in a population. If this occurs, there is no longer genetic variation for the gene.

POPULATION AFTER GENETIC DRIFTThere are now more recessive alleles in the population than before.

REPRODUCTIONIn this example, a heterozygous couple (Cc) could have two children that are homozygous recessive (cc), causing an increase in the proportion of recessive alleles in the population.

cleft chin (dominant)smooth chin (recessive)

Neither allele is related to reproductive success. Inheritance is based solely on chance.

5 digits per hand(recessive)

NEWLY FOUNDED POPULATIONThe new population will be dominated by the genetic features present in the founding members.

SOURCE POPULATIONAllele frequencies:

A group of individuals may leave a population and become the founding members of a new, isolated population.

>5 digits per hand(dominant)

AMISH

GENETIC DRIFT - FOUNDER EFFECTThe founding members of a new population can have different allele frequencies than the original source population and, consequently, the new population experiences evolution.

ARTICLE: The Amish and Founder Effect

GENETIC DRIFT - BOTTLENECK EFFECT Occasionally, famine or disease or rapid environmental change may cause the deaths of a large, random proportion of the individuals in a population.

SOURCE POPULATION

NEW POPULATION

All cheetahs living today can trace their ancestry back to a dozen or so individuals that happened to survive a population bottleneck about 10,000 years ago!

EXTREME AND RAPID ENVIRONMENTAL CHANGE

The new population will be dominated by the genetic features present in the surviving members.

SOME CATASTROPHE

Unless more individuals are introduced to the population, mating options will be limited thus

decreasing variation in the gene pool (decreasing genetic diversity).

LAB: Genetic Drift Activity

MECHANISMSOF EVOLUTION

MIGRATIONAfter a group of individuals

migrates from one population to another, both

populations can experience a change in their allele

frequencies and, consequently, experience

evolution.

MIGRATION (GENE FLOW)

1 BEFORE MIGRATIONTwo populations of the same species exist in separate locations. In this example, they are separated by a mountain range.

Population 1 Population 2

#3

2 MIGRATIONA group of individuals from Population 1 migrates over the mountain range.



migrates from one population to another, both populations can experience a change in their allele frequencies and, consequently, experience

evolution.



#3

3 AFTER MIGRATIONThe migrating individuals are able to survive and reproduce in the new population and they may experience evolutionary changes from population 1.



migrates from one population to another, both populations can experience a change in their allele frequencies and, consequently, experience

evolution.



#3

3 Conditions that must occur for Natural Selection

1. VARIATION OF A TRAIT IN A POPULATION

2. The trait must be inheritable

The tiniest dog in a litter has reduced differential reproductive success. Its more robust siblings prevent access to the food it needs to grow and thrive.

3. One version of the trait must be in greater abundance than a different version of the trait.

Mechanism of Evolution

Natural Selection

#4

Natural SelectionThere is indirect and direct evidence of

I. Indirect – we find it, not witness it

II. Direct – we are witness to the development of

Will be seen when there is:

1.Over population

2.Inheritance variation

3.Struggle for survival (abiotic factors too)Evidence:

1.Fossils 4. Embryos 2.Comparative Anatomy 5. Biogeography3.Adaptation 6. Field/lab Experiments

How long can a fruit fly survive without food?

?

“SURVIVAL OF THE FITTEST”—ONLY THE ‘BEST’ FLY WILL SURVIVE AND BE ABLE TO REPRODUCE AND PASS IT’S GENES ON TO THE NEXT

GENERATION.IT IS THEN SAID TO BE ‘FIT’-THIS IS NATURAL SELECTION.

AVERAGE STARVATION RESISTANCE

Hours until starvation

Num

ber

of f

lies The average fruit fly

can survive about 20 hours without food.

A MORE GENETICALLY ‘FIT’ FLY

GENETICALLY‘UNFIT’” FLY

Can fruit flies evolve so that they can resist starvation longer? Canwe see Natural Selection at work? (YES)

?

THE EXPERIMENT

= 500 fruit flies

Food removed

Food returned Eggs

New generation

1 INITIAL SETUPStart with a cage that contains a large number of fruit flies (5,000), and remove the food.

3 START NEW GENERATIONAfter the surviving flies eat a bit, collect the eggs those flies lay and transfer them to a new cage.

2 TESTING STARVATION RESISTANCEWait until 80% of the flies starve to death, then return the food to the cage. Record the average starvation-resistance time.

Only the most starvation-resistant flies live to lay eggs.

THE RESULTS




Num

ber

of f

lies

Num

ber

of f

lies

Num

ber

of f

lies

Experiment continues through 60 generations.

GENERATION 60Average starvation resistance: 160 HR.---this is evolution (change) at work

GENERATION 1Average starvation resistance: 20 HR.

GENERATION 2Average starvation resistance: 23 HR.

Over many generations of natural selection, the population changes! The flies now resist starvation much longer.

Peppered Moth Lab

Individuals with favorable Individuals with favorable traits are more likely to traits are more likely to leave more offspring better leave more offspring better suited for their environmentsuited for their environment

Example:Example:English peppered English peppered moth moth (Biston betularia)

Natural Selection

Peppered Moth Natural Selection Simulation Peppered Moth Natural Selection Simulation

Peppered Moth Natural Selection Simulation

BIOGEOGRAPHY: HAWAIIAN HONEYCREEPERS

The honeycreepers of Hawaii have adapted to a wide range of habitats, yet still closely resemble a finch-like shared ancestor found nearly 2,000 miles away---the major difference is the bill .

’I’iwihoneycreeper

Maui Parrotbillhoneycreeper

’Akeke’ehoneycreeper

Mainland finch(probablesharedancestor)

BIOGEOGRAPHY: HONEYCREEPERS---A MODERN DAY

DARWIN’S FINCH SCENARIO

Evidence of NS: Adaption

BIOGEOGRAPHY: AUSTRALIAN MARSUPIALS AND THEIR PLACENTAL COUNTERPARTS

AU

STR

AL

IAN

MA

RSU

PIA

LS

PL

AC

EN

TA

L C

OU

NT

ER

PA

RT

S

Tasmanian wolfNumbatSugar glider

Gray wolfGiant anteaterGray squirrel

Though less related to each other than you are to a shrew, these marsupials and their placental counterparts (both mammals) have come to resemble each other as natural selection has adapted them to similar habitats.

Evidence of NS: biogeography


NATURAL SELECTIONWhen these three conditions are satisfied, the population’s allele frequencies change and,

consequently, evolution by natural selection occurs.

1 VARIATIONFOR A TRAITDifferent traits are present in individuals of the same species

3 DIFFERENTIAL REPRODUCTIVE SUCCESSIn a population, individuals with traits most suited to reproduction in their environment generally leave more offspring than individuals with other traits.

2 HERITABILITYTraits are passed on from parents to their children.

EVOLUTION BY NATURAL SELECTION: A SUMMARY

1 VARIATION FOR A TRAIT

In a population, rabbits with slower running speeds are eaten by the fox and their traits are not passed on to the next generation.

The trait of running speed is passed on from parents to their offspring.

Running speed in rabbits can vary from one individual to the next.

2 HERITABILITY

3 DIFFERENTIALREPRODUCTIVE SUCCESS

Speed

NATURAL SELECTION IN NATURE

EVOLUTION OF ANTIBIOTIC RESISTANCE

Staphylococcus

1940s

Today

PenicillinKill zone

When first used as medicine in the 1940s, penicillin was uniformly effective in killing the bacterium Staphylococcus aureus. Today, natural selection has led to an increase in antibiotic-resistant alleles, and humans are increasingly at risk from untreatable Staphylococcus infections.(this is ongoing evolution taking place right now )

Very little of the Staphylococcus is killed.

Most of the Staphylococcus is killed.

EVOLUTION IN PROGRESS: GREEN GRASS ON A GOLF COURSE

Rough

LOWEST LOW HIGHSEEDPRODUCTION

SLOWEST SLOW RAPIDSEXUALMATURATION

SELECTIVEPRESSUREMonthly mowingschedule

Putting greenFairway

A single species of grass is planted on a golf course. On the putting greens, it is cut very frequently / on the fairways it is cut only occasionally / in the rough it is almost never cut at all.

Over the course of only a few years, grass plants from the same stock had developed into three distinct populations as a result of the frequency at which they were cut.

LIFE IS SHORTSO MUST

REPRODUCE RAPIDLY

WITH LARGESEED

PRODUCTION

Evolution does not work this way

LAB: Natural Selection

(Birds on an Island)

Purpose: •Explore how the frequencies of three beak phenotypes change over several generations in a population of bird on an island.

Lab Report Format

• Title

• Group Members

• Benchmark

• Problem

• Introduction

• Hypothesis

• Variables

• Data

Documents

EVOLUTION: PROCESSES & PATTERNS