Final Stretch!

Who was Charles Darwin?

HW: Begin Evolution Study Guide w/Word Bank

Agenda: 1. Turn in Genetic Disorder Brochures 2. Discuss EOCT Review Tue & Thur 3. Discussion: Charles Darwin and Theory of Evolution

Georgia Performance Standards:SB 5: Evaluate the role of natural selection in the theory of evolution

15.1 Darwin’s Theory of Natural Selection

Darwin on the HMS Beagle

Evolution

His job was to collect biological and geological specimens during the ship’s travel.

Chapter 15

What can explain the large extent of biological diversity on earth?

• Evolution – change over time– How life has changed over time

The Galápagos Islands

Evolution

Darwin began to collect mockingbirds, finches, & other animals on the 4 islands.

He noticed that the different islands seemed to have their own, slightly different varieties of animals. Later called descent with modification

15.1 Darwin’s Theory of Natural Selection

Chapter 15

The Galapagos Islands• West of South America• Group of islands each with

different climates• Tortoises varied from island to

island in neck length and shell shape

• Finches varied in beak shape• Characteristics of plants and

animals varied from island to island

Evolution

15.1 Darwin’s Theory of Natural Selection

Chapter 15

Darwin Continued His Studies

Evolution

Darwin inferred that if humans could change species by artificial selection, then perhaps the same process could work in nature. Think of Biotechnology and Agricultural

Engineering today!!

15.1 Darwin’s Theory of Natural Selection

Journal Entry January 7, 20101.How life has changed over time is:a.Natural Selection b. Descent with modification c. Evolution

2. According to Darwin, the fact that plants & animals may look similar but show variation is due toa. Natural Selection b. Descent with modification c. Evolution

3. The process, or driving force, that causes organism to gradually change in response to their environment is:b.Natural Selection b. Descent with modification c. Evolution

4. The use of biotechnology today can be considered an example of:a. Natural Selection b. Artificial Selection c. Derived trait

5. Charles Darwin took his voyage aboard the HMS _______________ and did most of his research in______________.a. Bagel; Australia b. Evolution; South Africa c. Beagle; Galapagos

What did Darwin call the process by which an individual changes over time?

Agenda: 1. Review: Natural Selection 2. Discuss Support/Evidence for Evolution

Georgia Performance Standards:SB 5: Evaluate the role of natural selection in the theory of evolution

Natural Selection

Evolution

Individuals in a population show variations. Variations can be inherited. Organisms have more offspring than can survive with

available resources.

Variations that increase reproductive success will have a greater chance of being passed on.

15.1 Darwin’s Theory of Natural Selection

Chapter 15

“Survival of the Fittest”

The Origin of Species

Evolution

Darwin published On the Origin of Species by Means of Natural Selection in 1859.

It is a means of explaining how evolution works.

15.1 Darwin’s Theory of Natural Selection

Chapter 15

Lamarck’s Theory• Pre-Darwin scientist• Inheritance of acquired traits due to use and disuse of features• Structures not used would shrivel and disappear• Early scientist to recognize that organisms had changed over

time

15.2 Evidence of Evolution

Support for Evolution

Evolution

The fossil record

Glyptodont

Provide a record of species that lived long ago.

Show that ancient species share similarities with species that now live.

Armadillo

Chapter 15

15.2 Evidence of EvolutionSupport for Evolution

Evolution

Biological Molecules Nucleotide changes (mutation) cause a change in amino

acid sequences Species with a common ancestor will have fewer

differences in their genes and amino acids.

Chapter 15

Geographic Distribution

Evolution

The distribution of plants and animals that Darwin saw first suggested evolution to Darwin.

Rabbit Mara

15.2 Evidence of Evolution

Chapter 15

Support for Evolution

Evolution

Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors.

Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms.

15.2 Evidence of Evolution

Chapter 15

Homologous StructuresAnatomically similar structures inherited from

a common ancestor

Evolution

Same function but different structure

NOT inherited fromcommon ancestor.

Analogous Structures

Chapter 15

Evolution

Vestigial Structures Structures that are the reduced

forms of functional structures in other organisms.

15.2 Evidence of Evolution

Chapter 15

Evolutionary theorypredicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost.

Evolution

Comparisons of the similarities in organisms are seen in comparative anatomy and in the fossil record.

Organisms with closely related morphological features have more closely related molecular features.

15.2 Evidence of Evolution

Chapter 15

More Terms• Fitness – ability of an individual

to survive and reproduce in a specific environment

• Adaptation – inherited characteristic that increases an organism’s chance of survival–Can be physical traits as well as behavioral traits

Evolution

Camouflage

Allows organisms to become almost invisible to predators

Leafy sea dragon

15.2 Evidence of Evolution

Chapter 15

Evolution

Mimicry

One species evolves to resemble another species.

Western coral snake California kingsnake

15.2 Evidence of Evolution

Chapter 15

Evolution

Natural Selection

Acts to select the individuals that are best adapted for survival and reproduction

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Stabilizing selection operates to eliminate extreme expressions of a trait when the average expression leads to higher fitness.

15.3 Shaping Evolutionary Theory

Chapter 15

Ex. Siberian Husky

Evolution

Directional selection makes an organism more fit.

15.3 Shaping Evolutionary Theory

Chapter 15

Favors the extremes Ex. Greyhound Dog

Evolution

Disruptive selection is a process that splits a population into two groups.

15.3 Shaping Evolutionary Theory

Chapter 15

Ex. Black, White, & Gray Rabbits

15.3 Shaping Evolutionary Theory

Mechanisms of Evolution

Evolution

Population genetics Hardy-Weinberg principle states that when allelic

frequencies remain constant, a population is in genetic equilibrium.

Chapter 15

Evolution

15.3 Shaping Evolutionary Theory

Chapter 15

Write these down & know these!

Evolution

Genetic Drift A change in the allelic frequencies in a population

that is due to chance and random mating

In smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater.

Marble Example

15.3 Shaping Evolutionary TheoryChapter 15

Evolution

Nonrandom Mating

Promotes inbreeding & could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Founder Effect

The loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population

15.3 Shaping Evolutionary Theory

Chapter 15

Mainland

Island 3

Island 2

Island 1

Evolution

Bottleneck a significant percentage of a population or species

is killed or otherwise prevented from reproducing and can rebound later

15.3 Shaping Evolutionary Theory

Often caused by a natural disaster

What is a gene pool?• Gene pool – combined genetic

info of all members of a population– Contains two of more alleles

(genes) for the same trait– Allele frequency – number of

times an allele occurs in a gene pool compared to the number of times another allele occurs (expressed in percents)

Sample Population

48% heterozygous

black

36% homozygous

brown

16% homozygous

black

Frequency of Alleles

allele for brown fur

allele for black fur

Relative Frequencies of AllelesSection 16-1

Gene Flow• Genes entering or leaving a population

• AKA. Migration– Emigration Genes LEAVING a population– Immigration INCOMING genes in a population

What are sources for genetic variation?

• Mutations – random change in the DNA, may cause evolution in future populations

• Genetic shuffling – occurs in meiosis when gametes are formed

Evolution

Sexual selection operates in populations where males and females differ significantly in appearance.

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Prezygotic isolation prevents reproduction by making fertilization unlikely.

Eastern meadowlark and Western meadowlark

15.3 Shaping Evolutionary Theory

Chapter 15

• In behavioral isolation, patterns of courtship may be different.

• In temporal isolation, different groups may not be reproductively mature at the same season, or month, or year.

• In ecological isolation, not in the same habitat where they are likely to meet.

Postzygotic isolation occurs when fertilization has occurred but a hybrid offspring cannot develop or reproduce.

Evolution

Prevents offspring survival or reproduction

Liger

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Allopatric Speciation

A physical barrier divides one population into two or more populations.

Abert squirrel Kaibab squirrel

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Sympatric Speciation

A species evolves into a new species without a physical barrier.

The ancestor species and the new species live side by side during the speciation process.

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Adaptive Radiation

Can occur in a relatively short time when one speciesgives rise to many different species in response to the creation of new habitat or some other ecological opportunity

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Coevolution

The relationship between two species might be so close that the evolution of one species affects the evolution of the other species.

Mutualism

Coevolutionary arms race

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Unrelated species evolve similar traits even though they live in different parts of the world.

Convergent Evolution

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

Rate of Speciation

Evolution proceeds in small, gradual steps according to a theory called gradualism.

Punctuated equilibrium explains rapid spurts of genetic change causing species to diverge quickly.

15.3 Shaping Evolutionary Theory

Chapter 15

Evolution

15.3 Shaping Evolutionary Theory

Chapter 15