Bellringer -March 12, 2014

Bellringer-March 12, 2014 Imagine a population of 200 birds, some red and some

yellow. The red allele, R, is dominant over the yellow allele, r. There are 72 RR birds, 96 Rr birds, and 32 rr birds in the population.

◦ What are the genotypic frequencies in the population?  

◦ What are the allelic frequencies in the population?  

◦ Using the frequencies you calculated in b, what would Hardy-Weinberg predict the genotypic frequencies should be? What about allelic frequencies? Is this population in Hardy Weinberg equilibrium?

ANSWER KEY RR = 72/200 = 0.36; Rr=96/200 = 0.48 ; rr= 32/200

= 0.16 R=72 + 72 + 96 = 240/400 = 0.6; r = 32 + 32 + 96 = 160/400 = 0.4 P=R= Red q= r = yellow 32/200= 0.16 = yellow = rr= q2

√0.16=√q2

q = 0.4 then p = 0.6 RR = p2 = (0.6)2 = 0.36 = 36.00% Rr = 2pq = 2(0.6)(0.4) = 0.48= 48.00% rr = q2 = (0.4)2 = 0.16 = 16.00%

Evolution and Speciation

(Macroevolution part 1)

Ms. KimH. Biology

Evolution on a small scaleChange in allele frequencies from one

generation to the nextA process that leads to a change in a

speciesNatural selectionGenetic DriftGene Flow MutationSexual Selection

Microevolution explains how populations evolve

What is microevolution?

What is Macroevolution?Origin of different species

SPECIATIONExtinction of speciesEvolution of major features

Protective Coloring◦ Camouflage and Mimicry

Physiological Adaptations◦ Reproductive/Hormonal Changes◦ Color changes

Behavioral Adaptations◦ Courtship dances/ songs◦ “Fighting” tactics

Also arise in response to environmental pressures◦ Temperature, Antibiotic/pesticide resistance

Types of Adaptations

Animals who have greater fitness survive in environment and live to reproduce

Random changes in DNA (mutations) can lead to greater or less fitness ◦ Produced by Sexual Reproduction◦ Allow for DIVERSITY in a Population

Adaptations allow an organism to survive better in their environment

Mechanism for change in a population of organisms

Directional◦Extreme form favored by natural selection

Stabilizing◦Middle form most successful

Disruptive◦Two extreme forms successful in separate environments

RECALL: 3 Types of Natural Selection

Types of Evolution1. Convergent evolution organisms that are NOT closely related

independently evolve similar traits as a result of having to adapt to similar environments.

2 species acquiring same characteristics from 2 different ancestral species

Ex: Dolphins & fishesEx: Wings of bees & bats

Analogous Structures

2. Divergent evolution 2 species gradually become different Often occurs when closely related species

diversify to new habitatsFormation of 2 descendent species from an ancestral speciesEx: Darwin’s finchesType: Adaptive radiation

Homologous structures

Adaptive Radiation Example of divergent

evolution Appearance of numerous species

over a short period of time Adapted species from a common

ancestor when they are introduced to new environmental opportunities

Typically occurs when a few organisms make their way to new, usually distant areas OR mass extinctions occur, which open up new niches

KAUAI5.1

millionyears OAHU

3.7millionyears

HAWAII0.4

millionyears

1.3millionyears

MAUIMOLOKAI

LANAI Argyroxiphium sandwicense

Dubautia linearisDubautia scabra

Dubautia waialealae

Dubautia laxa

N

Hawaiian archipelago Example of adaptive radiation

What type of evolution?

A.Divergent B.ConvergentC.Coevolution

What type of evolution?

A. Divergent B. ConvergentC. Coevolution

3. Coevolution 2 organisms evolve (change) in

response to each other Insects and the flowers (ex: orchids)

they pollinate

4. Parallel Evolution 2 species evolve independently of

each other, maintaining similar traits

Usually occurs between unrelated species (but similar ancestors) that do NOT occupy the same or similar habitats◦Ex: Eutherians (placental) and

Marsupial mammals

What type of evolution?

A. Divergent B. ConvergentC. Parallel Evolution

What is Speciation?Origin of new

species

How would we identify if a species is “new”?

Anagenesis (phyletic evolution) ◦transforms one species into another

Cladogenesis (branching evolution)◦ the splitting of a gene pool, giving rise to one or more new species

Two Basic Patterns of Evolutionary Change

LE 24-2

Anagenesis Cladogenesis

Gradualism◦Species change slowly (gradually) over time

Punctuated Equilibrium◦Species can make rapid “leaps” in evolution

How fast does evolution occur?

TimeGradualism model Punctuated equilibrium model

What is a Species? Species is a Latin word meaning “kind” or “appearance”◦A population of organisms that produces viable fertile offspring in nature.

◦They can NOT interbreed with other populations

Example 1CASE 1A mule is the offspring of a female horse

and a male donkey. In contrast, the hinney is the offspring of a male horse and female donkey. The mule is easier to breed and larger in size than the hinney. For these reasons, the mule became an important domesticated animal. Horses have 64 chromosomes, donkeys have 62. The mule has 63 and cannot evenly divide, that is why the animal is sterile.

Example 2CASE 2A liger is a cross between a female tiger

and a male lion. In contrast, the tigon is a cross between a male tiger and a female lion. These two species do not breed in nature because their habitats are so different. Lions live in open grasslands while tigers live in forests. In captivity, it is possible to produce ligers and tigons. Male ligors are sterile, but female ligers are fertile and may reproduce with either tigers or lions.

Example 3CASE 3E.coli is a bacterium normally found in

the intestines. It is harmless and may actually be beneficial to the human digestive system. There is a pathogenic strain of E.coli that produces a toxin that can kill its human host. The two strains look very similar under a microscope. Comparison of their genomes reveals that the pathogenic strain lacks 528 genes found in the normal strain and has 1,387 genes not found in the normal strain.

What are other species concepts?

5 Types:Morphological

Group of individuals sharing similar characteristicsRecognition

Behavior/chemical recognition between individualsGenetic

Range of variation in DNA- similar in individualsCladistic

Species defined as a branch in a cladogramBiological

Group of individuals capable of interbreeding

Similarity between different species different behaviors and songs

Diversity within a species defined by capacity to interbreed.

Speciation = the origin of new species◦ Must explain how new species originate and how

populations evolve Microevolution (genotype evolution)

◦ adaptations that evolve within a population’s gene pool

Macroevolution (phenotype evolution)◦ refers to evolutionary change at the population

level◦ Major biological changes evident in the fossil

record

Speciation