Unit 4 EvolutionCH 10: Principles of Evolution

Ch 11: Evolution of PopulationsCh 12: The History of Life

Ch 10 Principles of Evolution10.1 Early ideas about evolution

• Scientists:– Carolus Linneaus: Swedish botanist, developed

classification system (binomial nomenclature) for species

– Georges Louis Leclerc de Buffon: French naturalist, suggested species shared ancestors, he and Charles Lyell suggested earth was much oder then 6000yrs

– Erasmus Darwin: Charles’ grandfather, English doctor/ poet, proposed living things from common ancestor

10.1 cont’d

– Jean-Baptiste Lamarck: French naturalist, proposed all organisms evolved towards perfection/ complexity b/c of change in enviro.

• Leading up to Darwin’s theory– Georges Cuvier: French zoologist, fossils different

in layers and catastrophism– James Hutton: Scottish geologist, proposed

gradualism– Charles Lyell: English geologist, agreed and theory

of uniformitarism

10.2 Darwin’s observations• Island species differences

– Variation was interspecific and intraspecific based on islands he visited

– Galapagos Islands: tortoises (necks/ legs), finches (size beak)

Darwin’s observations cont’d• Fossil/ geologic evidence

– Giant armadillo fossils; suggested ancestor and earth older 6000yrs

– Marine fossils in mountains; volcanoes/ other activity changed land over time (gradualism)

– Darwin and His Work

10.3 Theory of Natural Selection• Artificial selections- people make genetic

diversity of plants/animals• Natural selection

– Darwin- heredity; Malthus- struggle for survival/ competition

neck feathers

crop

tail feathers

• 4 principles of Natural Selection:– Variation: inherited/ mutations– Overproduction: many offspring= survival or

compete– Adaptation: better suited for environment– Descent with modification: better trait passed on– “fitness”: ability to survive in environment/ adapt

wrist bone

five digits

10.3 cont’d• Natural selection changes phenotypes not

genotypes• Why evolve?

– Changing environments: ex food/ finches– Not really ‘passed on’ over many generations, can

be response to need in environment

– Natural Selection

Quick Data Lab Pg 290

10.4 Evidence of Evolution• Evidence/ support

– Fossils: age/ location/ environment when organism was alive; layers had oldest at bottom

– Geography: Galapagos similar plants/ animals as S. America; distance from mainland, biogeography

Human hand

Bat wing

Mole foot

Fly wing

– Embryology: crab/ barnacles look alike as larva; embryos in verts. Look similar too

– Anatomy: homologous structures (forelimbs)- look same but have different functions; analogous structures (wings)- do the same function, but look very different; vestigial structures (ostrich/snake)- organs or structures had function for earlier ancestors

Human hand Bat wingMole foot

10.5 Evolutionary Biology Today• Paleontology- fossils/ extinct organisms; NEW

and lacked transitional fossils

• Fossil/ anatomical evidence– DNA sequence analysis: nucleotides show how

closely related– Pseudogenes: no longer function but still in DNA

(like vestigial organs)– Homeobox genes: control development of specific

structures- links us back to common ancestor– Protein comparisons: molecular fingerprinting to

show common cells and make ancestor connections

Videos of Evolutionary Biology

• Evolution is in all biology fields!

• Natural Selection

• Evolutionary Bio 1

• Evolutionary Bio 2

End of CH 10 Review

• Pick 2 of the following to complete• Title the page “Ch 10 review” and keep it in

your classwork section.

1. Student Premium: Animated Biology clips2. Student Premium: Virtual Investigation3. Student Premium: Interactive Review Games

11.1 Genetic Variation within Popln• Genetic variation leads to phenotypic variation.• Phenotypic variation is necessary for natural selection.• Genetic variation is stored in a population’s gene pool.

– made up of all alleles in a population– allele combinations form when organisms have offspring

Genetic variation comes from several sources.

• Mutation is a random change in the DNA of a gene.

• Recombination forms new combinations of alleles.

– can form new allele– can be passed on to

offspring if in reproductive cells

– usually occurs during meiosis – parents’ alleles

arranged in new ways in gametes

11.2 Natural Selection in Popln• A normal distribution

graphs as a bell-shaped curve.– highest frequency

near mean value

– frequencies decrease toward each extreme value

• Traits not undergoing natural selection have a normal distribution.

Natural Selection changes poplns• Microevolution is evolution within a population.

(observable change in the allele frequencies)• Directional selection favors phenotypes at one

extreme.• Stabilizing selection favors the intermediate

phenotype.• Disruptive selection favors both extreme phenotypes.

• Directional selection

• Stabilizing selection

• Disruptive selection

11.3 Other Mechanisms of Evolution• Genetic drift causes a loss

of genetic diversity.• It is most common in small

populations.• A population bottleneck can

lead to genetic drift. – It occurs when a few

individuals start a new population.

– The founder effect is genetic drift that occurs after start of new population.

Genetic drift has negative effects on a population.– less likely to have some individuals that can adapt – harmful alleles can become more common due to

chance

There are two types of sexual selection.– intrasexual selection: competition among males– intersexual selection: males display certain traits

to females

11.4 Hardy-Weinberg Equilibrium– very large population: no

genetic drift – no emigration or immigration:

no gene flow – no mutations: no new alleles

added to gene pool– random mating:

no sexual selection– no natural selection:

all traits aid equallyin survival

• p2 + 2pq + q2 = 1

"The Hardy-Weinberg equation is based on Mendelian genetics. It is derived from a simple Punnett square in which p is the frequency of the dominant allele and q is the frequency of the recessive allele."

11.5 Speciation through isolation• Populations become isolated when there is no

gene flow. – Isolated populations adapt to their own

environments.– Genetic differences can add up over generations.

• Reproductive isolation can occur between isolated populations.

• Behavioral barriers can cause isolation.– called behavioral isolation– includes differences in courtship or mating behaviors

• Speciation is the rise of two or more species from one existing species.

• Geographic barriers can cause isolation.– called geographic isolation– physical barriers divide population

• Temporal barriers can cause isolation.– called temporal isolation– timing of reproductive periods prevents

mating

11.6 Patterns of evolution• Natural selection can

have direction.• Convergent evolution:

evolution similar traits in unrelated species.

• Divergent evolution: evolution toward different traits in closely related species.

• Mass extinctions are rare but much more intense.– destroy many species at global level– thought to be caused by catastrophic events– at least five mass extinctions in last 600

million years

• Many species evolve from one species during adaptive radiation.– ancestral species

diversifies into many descendent species

– descendent speciesusually adapted towide range ofenvironments

Ch 12 The History of Life12.1 The Fossil Record

How Fossils Form:• Permineralization: minerals carried by water are

deposited around a hard structure.– Natural cast forms: flowing water removes all of the original

tissue, leaving an impression.• Amber-preserved fossils: organisms that become trapped

in tree resin that hardens after the tree is buried.• Preserved remains form when an entire organism

becomes encased in material such as ice.• Only a tiny percentage of living things became

fossils!!

Radiometric Dating:• Relative dating estimates the time during

which an organism lived.– It compares the placement of fossils in layers of

rock.• Radiometric dating uses decay of unstable

isotopes.– Isotopes are atoms of an element that differ in

their number of neutrons

Half-Lives

12.2 The Geologic Time Scale

• Index fossils can provide the relative age of a rock layer. – existed only during specific spans of time– occurred in large geographic areas

• Index fossils include fusulinids and trilobites. • The history of Earth is represented in the

geologic time scale.

• Eras last tens to hundreds of millions of years.– consist of two or

more periods– three eras:

Cenozoic, Mesozoic, Paleozoic

• Periods last tens of millions of years.– most commonly used units of time on time

scale– associated with rock systems.

• Epochs last several million years.

12.3 Origin of Life• The most widely

accepted hypothesis of Earth’s origins is the nebula hypothesis.

• There are two organic molecule hypotheses.– Miller-Urey experiment:

test input of E from light– meteorite hypothesis: off

Australia, had 90aa found on Earth

electrodes

heat source amino acids

water

“atmosphere”

“ocean”

• There are different hypotheses of early cell structure.– iron-sulfide bubbles hypothesis

• Martin/Russell proposed• Conditions needed for early life

– lipid membrane hypothesis• Crucial step in the origin of life!

• A hypothesis proposes that RNA was the first genetic material.

– Ribozymes are RNA molecules that catalyze their own replication.

– DNA needs enzymes to replicate itself.

12.4 Early Single-Celled Organisms

• Microbes have changed the physical and chemical composition of Earth.

• The oldest known fossils are a group of marine cyanobacteria. – prokaryotic cells– added oxygen to

atmosphere– deposited minerals

• Fossil stromatolites provide evidence of early colonies of life.

• Endosymbiosis is a relationship in which one organism lives within the body of another.

• Mitochondria and chloroplasts may have developed through endosymbiosis.

• Genetic variation is an advantage of sexual reproduction.

• Sexual reproduction may have led to the evolution of multicellular life.

12.5 Radiation of Multicellular Life• Life moved onto land

during the Paleozoic Era.• Multicellular organisms

first appeared during the Paleozoic era.

• The era began 544 million years ago and ended 248 million years ago.

• The Cambrian explosion led to a huge diversity of animal species.

Reptiles radiated during the Mesozoic era.

• The Mesozoic era is known as the Age of Reptiles.• It began 248 million years ago and ended 65 million years ago.• Dinosaurs, birds, flowering plants, and first mammals

appeared.

Mammals radiated during the Cenozoic era.

• The Cenozoic era began 65 million years ago and continues today.

• Placental mammals and monotremes evolved and diversified.

• Anatomically modern humans appeared late in the era.

12.6 Primate Evolution• Primates are mammals with flexible hands and

feet, forward-looking eyes and enlarged brains.

• Primates evolved into prosimians and anthropoids.– Prosimians are the oldest living primates.– They are mostly small and nocturnal.

– They are subdivided into the New World monkeys, Old World monkeys, and hominoids.

– Anthropoids are humanlike primates.

– Homonoids are divided into hominids, great apes, and lesser apes.

– Hominids include living and extinct humans.

• Bipedal means walking on two legs.– foraging– carrying infants and food– using tools

• Walking upright has important adaptive advantages.

Modern humans arose about 200,000 years ago.

• Homo sapiens fossils date to 200,000 years ago.• Human evolution is influenced by a tool-based culture.• There is a trend toward increased brain size in hominids.

Australopithecusafarensis

Homo habilis Homo neanderthalensis

Homo sapiens