Theory of Evolution

Evolution Notes 2010

History of Life

Chapter 19

536-568

1

KEY Terms Chap 16, 17, and 19

• Evolution

• Fossil

• Artificial selection

• Adaptation

• Fitness

• Natural selection

• Biogeography

• Homologous structure

• Analogous structure

• Vestigial structure

• Darwin

• Lamark

• Cuvier

• Lyell

• Superpostion

• Relative age

• Absolute age

• Biogenesis

• Spontaneous Generation

• Extinct

• Paleontologist

• Radiometric dating

• Half-life

• Macroevolution

• Gradualisms

• Punctuated equilibrium

• Adaptive radiation

• Convergent evolution

• Co evolution

• Endosymbiotic theory

Evolution Notes 2010 2

Biogenesis

• All living things come from other living things, seems reasonable to us today.

Before the 17 century it was widely thought that living things could also arise from nonliving things in a process called spontaneous generation.

This seemed to explain why maggots appeared on rotting meat and why fish appeared in ponds that were dry the previous season


Redi’s Experiment

• 1626-1697 Italian scientist Francesco Redi

• Studied developmental forms of flies

• Did flies generate spontaneously from rotting meat?

• Experiment control group rotting meat left open  maggots, experimental group rotting meat sealed  no maggots

• Flies come from eggs laid by other flies



Redi’s Experiment

5

Spallanzani Experiment

• 1729-1799 Italian scientist Lazzaro

Spallanzani

• Microorganisms formed not from air but from other microorganisms

• Boiled broth, control open becomes cloudy, experimental group sealed remains clear

• Those that believed in spontaneous gen found flaws in his experiment, continued to believe in SG


Spallanzani Experiment


Pasteur’s Experiment

• 1800s Paris Academy of Science offered a prize to anyone who could clear up the issue once and for all

• Louis Pasture (1822-1895) won

• Pasture used similar format of Spallanzani except he used a curve neck flask no growth for one year till the curve was broken and allowed for microorganisms from the air to enter

 No longer believed in spontaneous generations but  biogenesis (to live to be born)



Pasteur Experiment

9

Theories of life's origin


Earth’s History

• If spontaneous generation does not happen on Earth today, then the question remains: How did cell-based life arise in the first place? Key to answering this question lies in scientific hypotheses that conditions on early Earth were very different from present conditions.

Scientists continue to form and test these hypotheses by modeling conditions and process that could have given rise to the first cellular life form.


Formation of Earth

• Our solar system was a swirling mass of gas and dust

• Pulled together by gravity and formed the sun

• Planets formed through repeated collision of this space debris

Earths age

• More than 4 billion years ago

• Studying layers of sedimentary rock


Radiometric Dating

• Use of isotopes (change in # of neutrons)

• Mass number is the # of protons and neutrons

• Radioactive decayisotopes are unstable and release particles and energy

• Radioactive isotopes occur naturally in all matter

• Half-life - time it takes to decay, measure the amount


Radiometric Dating

– The half-life of potassium-40 is

1.26 billion years.


•

Radiometric Dating

Carbon-14 is a radioactive form of carbon naturally found in the atmosphere. It is taken up by living organisms along with “regular” carbon, so it can be used to date material that was once alive, such as bones or wood.

• After an organism dies, carbon-14 in its body begins to decay to nitrogen-14, which escapes into the air.

• Researchers compare the amount of carbon-14 in a fossil to the amount of carbon-14 in the atmosphere, which is generally constant. This comparison reveals how long ago the organism lived.

• Carbon-14 has a halflife of only about 5730 years, so it’s only useful for dating fossils no older than about 60,000 years .


First Organic CPDS

• Soviet Alexander I. Oparin (1894-1980) and

American John B.S. Haldane (1892-1964)

• Believed that earth early atmosphere contained ammonia, hydrogen gas, wand water vapor, carbon and hydrogen cpds

• At high temperatures gases would formed simple organic cpds such as amino acids

• Earth cooled water vapors condensed and created water systems

• Lighting fueled energy  creating macromolecules essential to life (proteins)


Synthesis of organic cpds

• 1953 Stanley Miller and Harold Urey set up and experiment to test the hypothesis

• Used gases that were assumed present in the earths atmosphere, using an electrical spark to simulate the lighting the experiment produced variety of organic compounds including amino acids


http://www.ucsd.tv/miller-urey/ http://www.wwnorton.com/college/chemistry/chemconnections/Origins/pages/spark.html


Beyond earth

• Some scientists believe that organic compounds could have been carried to

Earth by debris from space

• Studied 1970 meteorite


From molecules to cell-like structures

• Fox (1912-1998) studied cell structures

• Some from spontaneously in the lab from solution of simple organic chemicals

• Microspheres - spherical in shape and composed of many protein

• Coacervates -collection of droplets that are composed of molecules of different types

 Do not have all the properties of life!!


Origin of Heredity

• DNA  RNA  protein

• Believed that RNA molecules behave like proteins and catalyze chemical reactions

• Chech’s found that ribozymes could act as catalyst for their own replication  support the hypothesis that life could have started with self-replicating molecules of RNA


First cells

• Little or no oxygen existed on early earth

• Oldest fossils that are size and shape of some prokaryotes

• Developed in environments filled with organic molecules

• Believed they were anaerobic, heterotrophic prokaryotes


chemosynthesis

• Archaea- unicellular organisms, live in extreme harsh environments

• Tend to be autotrophic

• Obtain energy by chemosynthesis, oxidation of various inorganic substances

(sulfur)


Photosynthesis and aerobic respiration

• 3 billion yr ago

• Oldest know fossils similar to cyanobacteria (unicellular prok, photosynthesis), stromatolites (3.5 billion years old)

• Creation of ozone

• Endosymbiosis (mitochondria, chloroplasts)


The first Eukaryotes:

Endosymbiosis

(together, way of life)

(mitochondria, chloroplasts)



Theory of Evolution

Chapter 16

448-474

26

Review

• What is Genotype and phenotype

• Don’t forget that an organisms phenotype depends on an organisms genotype

• Can you explain how DNA in an organism determines the structure and function of protein that a cell produces


Objectives

• Define the biological process of evolution

• Summarize the history of scientific ideas about evolution

• Described Charles Darwin’s contributions to scientific thinking about evolution

• Analyze the reasoning in Darwin's theory of evolution of by natural selection

• Relate the concepts of adaptation and fitness to the theory of natural selection.


What was Charles Darwin’s contribution to science?

•

• Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors.

Charles Darwin was born in England on

February 12, 1809. He grew up at a time when the scientific view of the natural world was shifting dramatically.


History of Evolutionary Thought

• In the 1830s, the young English naturalist

Charles Darwin took a trip around the world on a shop called HSM Beagle.(5 years) He was fascinated by diverse and unique organisms, such as the giant tortoises of the Galapagos Islands. Darwin went ton to form one of the most important theories in biology.



Observations Aboard the

Beagle

What three patterns of biodiversity did Darwin note?

– Darwin noticed that some fossils of extinct animals were similar to living species.

– As he traveled, Darwin noticed three distinctive patterns of biological diversity: (1) Species vary globally, (2) species vary locally, and (3) species vary over time.


The Idea of Evolution

• Animals varied from island to island

• Organisms changed over time

• Development of new types of organisms from preexisting types of organisms over time

(Evolution)

• Heritable change in the characteristics within a population from one generation to the next

• Theory is something that takes observations, inferences, and tested hypotheses over time


Ideas of Darwin’s Time

• 18 century most scientists thought that all species were permanent and unchanging

• Once believed the earth was only thousands – not billion years old

• Evidence was emerging that organisms were changing over time

• http://www.youtube.com/watch?v=wl68aaiHdGo&feature=related

• http://www.youtube.com/watch?v=cbhvfDA5Vjs&feature=related

• http://www.youtube.com/watch?v=1NAKg46s1DA&feature=related


Ideas about Geology

• Strata – rock layers, being studied

• Found fossils in the strata

• Cuvier (1769-1832) spent years reconstructing organisms from fossil bones

• Found sudden changes from rocks to rocks

• Catastrophismsudden geologic catastrophes caused the extinction of large group of organism in the past (geologic change  extinction)

• Lyelluniformitarianism, geologic process that have changed the shape of Earth’s surface in the past continue to work in the same ways


Lamarck’s Ideas on Evolution

• French biologist (1744-1829)

• Organisms change over time

• Could acquire traits during the life time and pass it on to the offspring  inheritance of acquired characteristics


Darwin’s Ideas

• The Origin of Species by Means of Natural Selection

• Descent with Modifications was used to describe the process of evolution

• Must have descended by reproduction from preexisting species and that species must be able to change over time

• Was the first to argue that all came from first few species

• http://www.aboutdarwin.com/

• http://www.pbs.org/wgbh/evolution/darwin/origin/index.ht

ml



Darwin Finches

38

Evolution by Natural

Selection

Under what conditions does natural selection occur?

–

Natural selection occurs in any situation in which more individuals are born than can survive (the struggle for existence), there is natural heritable variation (variation and adaptation), and there is variable fitness among individuals (survival of the fittest).

– , Darwin realized that if more individuals are produced than can survive, members of a population must compete to obtain food, living space, and other limited necessities of life.

– Darwin described this as the struggle for existence


Natural Selection

mechanisms for descent with modifications

4 main parts

1. Overproduction

2. Genetic variation

3. Struggle to survive

4. Differential reproduction


1. Overproduction

• More offspring can be produced than can survive to maturity

• Humans: war, disease, lack of food

• Environment limits the populations of all organisms by causing death or by limiting successful births


Genetic variation and survival

2.GV

• Population individuals have different traits

• Some can be inherited

• Occasionally new traits may appear

3.Struggle to survive

• Compete among population “struggle for existence”, can improve or reduce chance

• Adaptation- makes survival a success


Variation and Adaptation

– Darwin knew that individuals have natural variations among their heritable traits, and he hypothesized that some of those variants are better suited to life in their environment than others.

– Any heritable characteristic that increases an organism’s ability to survive and reproduce in its environment is called an adaptation.

– Adaptations can involve body parts or structures, like a tiger’s claws; colors, like those that make camouflage or mimicry possible; or physiological functions, like the way a plant carries out photosynthesis

– The scarlet king snake exhibits mimicry—an adaptation in which an organism copies, or mimics, a more dangerous organism.

Although the scarlet king snake is harmless, it looks like the poisonous eastern coral snake, so predators avoid it, too.


4.Differential reproduction

• Organisms with the best adaptations are most likely to survive and reproduce  through inheritance the adaptations become more frequent in the populations

• Over time the populations begin to change

• Natural selection  nature changes the species by selecting traits

• Survival of the fittest- individuals hereditary


Survival of the Fittest

• According to Darwin, differences in adaptations affect an individual’s fitness.

• Fitness describes how well an organism can survive and reproduce in its environment.

• Individuals with adaptations that are well-suited to their environment can survive and reproduce and are said to have high fitness.

• Individuals with characteristics that are not well-suited to their environment either die without reproducing or leave few offspring and are said to have low fitness.

• This difference in rates of survival and reproduction is called

survival of the fittest. In evolutionary terms, survival means reproducing and passing adaptations on to the next generation.



Natural Selection

46

Natural Selection

– This hypothetical population of grasshoppers changes over time as a result of natural selection.

– Grasshoppers can lay more than 200 eggs at a time, but only a small fraction of these offspring

47


– Certain variations, called adaptations, increase an individual’s chances of surviving and reproducing.

– In this population of grasshoppers, heritable variation includes yellow and green body color.

– Green color is an adaptation: The green grasshoppers blend into their environment and so are less visible to predators.



– Because their color serves as a camouflage adaptation, green grasshoppers have higher fitness and so survive and reproduce more often than yellow grasshoppers do.



–

Green grasshoppers become more common than yellow grasshoppers in this population over time because more grasshoppers are born than can survive, individuals vary in color and color is a heritable trait, and green grasshoppers have higher fitness in this particular environment



– Natural selection does not make organisms

“better.” Adaptations don’t have to be perfect —just good enough to enable an organism to pass its genes to the next generation.

– Natural selection also doesn’t move in a fixed direction. There is no one, perfect way of doing something. Natural selection is simply a process that enables organisms to survive

51

Common Descent

– Darwin based his explanation for the diversity of life on the idea that species change over time.

– For evidence of descent with modification over long periods of time, Darwin pointed to the fossil record.

– This page from one of Darwin’s notebooks shows the first evolutionary tree ever drawn.

This sketch shows Darwin’s explanation for how descent with modification could produce the diversity of life.

– A single “tree of life” links all living things.


Objectives

• Relate several inferences about the history of life that are supported by evidence from fossils and rocks.

• Explain how biogeography provides evidence that species evolve adaptations to their environments.

• Explain how the anatomy and development of organisms provide evidence of shared ancestry.

• Compare the use of biological molecules with other types analysis of evolutionary relationships.

• Describe the ongoing development of evolutionary theory


Evidence of Evolution

• Many kinds of evidence give insight into the history of life n Earth and the patterns of change among organisms. Fossils that are different from organism living today are strong evidence that organisms on

Earth can change over time. But evidence of evolution is also found inside living organisms.


1. Fossil Record

is the remains of traces of an organism that died long ago

• Superposition - if the rock strata at a location have not been disturbed, the lowest stratum was formed before the strata above it, geologic time scale

• Relative ageage compared to that of other fossils

• Absolute ageuse radiometric dating, time since formation


Distribution of Fossils

Inferences

1.

that diff organism live at diff times

2. Today's organisms are diff from past

3. Adjacent layers are similar than ones below or above

4. Where they lived, existed, adapted




Geologic Time Scale

– Geologists and paleontologists have built a time line of

Earth’s history called the geologic time scale.

– The basic divisions of the geologic time scale are eons, eras, and periods.


Transitional species

• Features that are intermediate between those of hypothesized ancestors and later descendant species

• Once believed whales had legs


Recent Fossil Finds



The limb structure of

Ambulocetus (“walking whale”) suggests that these animals could both swim in shallow water and walk on land.



The hind limbs of Rodhocetus were short and probably not able to bear much weight.

Paleontologists think that these animals spent most of their time in the water.



– Basilosarus had a streamlined body and reduced hind limbs.

These skeletal features suggest that

Basilosarus spent its entire life swimming in the ocean.



– Modern whales retain reduced pelvic bones and, in some cases, upper and lower limb bones. However, these structures no longer play a role in locomotion.



– Other recent fossil finds connect the dots between dinosaurs and birds, and between fish and four-legged land animals.

– All historical records are incomplete, and the history of life is no exception. The evidence we do have, however, tells an unmistakable story of evolutionary change.


2.Biogeography

• Study of the locations of organisms around the world

• Organisms seemed closely related yet were adapted to different environments in nearby regions

• Yet some organisms seemed unrelated and had similar adaptations


3.Anatomy and 4.Embryology

• Anatomy- the study of the body structure of an organism

• Embryology - the study of how organism develop

• Homologous structuressimilar structures with common ancestors  diff functions

• Analogous structuresrelated functions  not derived from the same ancestral structure

• Vestigial structuresno longer have function



Vestigial structures



5.Biological Molecules (DNA)

• The greater the number of similarities between any given species, the more closely the species are related trough a common ancestor

• New information  constant debate

• Modern synthesis of evolutionary theory

• Many aspects are still poorly understood or unexplained

• We use phylogeny to so relationships

(classification)



Objectives

• Describe how convergent evolution can result among different species.

• Explain how divergent evolution can lead to species diversity

• Compare artificial selection and natural selection

• Explain how organisms can undergo convolution.


Evolution in Action

• Evolution is a continuous process.

Evolution is going on today in populations of living species and can be observed, recorded, and tested. Patterns of evolution repeat in different times and places.

Interactions between species , including humans, affect their ongoing evolution.


Types of evolution

• Convergent - different species evolve similar traits

• Divergent - descendants of a single ancestor diversify into species that each fit diff parts of the environment

• Adaptive radiationnew population in a new environment will undergo divergent evolution until the population fills many parts of the environment

• Artificial selectionpick traits

• Co evolutiontwo or more species have evolved adaptation to each other’s influence


Chapter 17 Evolution of

Populations

For extra help go to: http://bioactive.mrkirkscience.com/submenus/part4index.html

p. 480-504


Objectives

• Identify traits that vary in populations and that may be studied.

• Explain the importance of the bell curve to population genetics

• Compare three causes of genetic variation in a population

• Explain Hardy-Weinberg genetics equilibrium


Genetic Equilibrium

• By the time of Darwin’s death, in 1882, the idea of evolution by natural selection had gained wide acceptance among scientists.

Within the next century, an increasing scientific understanding of genetics became strongly linked with theories of evolution and natural selection.


Variation of Traits within a population

• Population - consists of a group of individuals of the same species that routinely interbreed, smallest unit in which evolution occurs

• Population geneticsstudy of evolution from a genetic point of view

• Microevolution - change in the collective genetic material of a population

• Populations can vary in traits (bell curve)


Causes of Variation

1. Environmental factors (food)

2. Heredity

3. Range of phenotypic possibilities (body sizes)

4. Mutation- random change in genes

5. Recombination- reshuffling of genes

6. Random paring of gametes


Hardy-Weinberg Equilibrium

Gene PoolUsed to describe the total genetic information available in a population

Based on a set of assumptions about an ideal hypothetical population that is not evolving (theoretical state)

1.

No net mutations occur

2.

Individuals neither leave or enter

3.

Populations are large

4.

Individuals mate randomly

5.

Selection does not occur


Objectives

• List five conditions under which evolution takes place

• Explain how migration can affect the genetics of populations

• Explain how genetic drift can affect population of different sizes

• Contrast the effects of stabilizing selection, directional selection, disruptive selection on populations over time

• Identify examples of nonrandom mating


Disruption of Genetic Equilibrium

• Evolution is the change in a population’s genetic material over generations, a change of the population’s alleles frequency or genotype frequency. Any exception to the fiver conditions necessary for Hardy-Weinberg equilibrium can result in evolution.

• Web 13d


mutation

• Very low rates under normal conditions

• Environmental factors can influence

• Change genetic equilibrium- new alleles

• Natural selection works slowly

• (first rule to HW)


Gene Flow

• Second rule to HW- no one leaves/enters

• Where they go so does the traits

• Immigration - movement into a population

• Emigrating - movement out of a population

• Gene flowprocess of genes moving from one population to another, migration of individuals or dispersal of seeds or spores


Genetic Drift

• Third law- pop large

• Genetic Driftrandom change in allele frequency

• Failure of even a single organism to reproduce can significantly disrupt the allele frequency of the population

• Small pop lager impact

 bottleneck effect

 founder effect


Types Genetic Drift

Founder Effect

• Two groups from a large, diverse population could produce new populations that differ from the original group.

bottleneck effect

• is a change in allele frequency following a dramatic reduction in the size of a population.


Nonrandom Mating

• 4 th rule- random mating

• Often influence by location

• Traits similar to own-Assortative mating

Sexual selection- picking a mate bases on looks or certain traits


Natural selection- 5

th

rule

1. Stabilizing selectionavg form of a trait have the highest fitness

2. Disruptive selectionindividuals with either extreme variation of a trait have greater fitness that individuals with the avg form of the trait

3. Directional selectionindividuals that display a more extreme form of a trait have greater fitness than individuals with an avg form of the trait




objectives

• Relate the biological species concept to the modern definition of species

• Explain how the isolation of populations can lead to speciation

• Compare two kinds of isolation and the pattern of speciation associated with each

• Contrast the model of punctuated equilibrium with the model of gradual change


Formation of Species

• How many species of organisms exist on Earth today?

• Undiscovered species may be so numerous that we have no accurate answer. Even small areas of tropical rain forest can contain thousands of species of plants, animals, and microorganisms.

• New species are discovered and others become extinct at an increasing rate.

• How can one species become two through speciation?


Concept of species

• Speciation - existing species are essentially changed version of older species, results in closely related species, can become diff over time

Morphological concept of species

• Morphology - internal/ external structures and appearance of an organism, used to classify species

Biological species Concepta species is a pop of organisms that can successfully interbreed but can not breed with other groups



Speciation

96

Isolation and speciation

4 major types

• Geographic isolation

• Allopatric speciation

• Reproductive isolation

• Sympatric speciation


Geographic isolation

• Physical separation of members of a population

• Habitat becomes divided, geographic barriers

• Gene flow stops

• Natural selection and genetic drift cause pop to diverge  incompatible for mating


Allopatric Speciation

• Happens when species arise as a result of geographic isolation, “different homelands”

• No longer a gene flow

• Genetic drift, mutations, natural selection

• Small populations

• Could still produce fertile offspring?


Allopatric speciation- Geographic isolation

• http://wps.prenhall.com/esm_freeman_biosci_1/7/1951/499633.cw/i ndex.html


Geographical and temporal isolation

• http://bioactive.mrkirkscience.com/19/ch19c1.html


Reproductive Isolation

• Barriers to successful breeding between populations groups in the same area

Two types

1. Prezygotic isolationbefore fertilization

2. Postzygotic - after fertilization


Prezygotic barriers- isolation

Prevent mating or fertilization

• Temporal - mating or flowering occurs at different season or times of day

• Habitat – populations live in different habitats and do not meet

• Behavioral - there is little or no sexual attraction between different species

• Mechanical – structural differences in genitals or flowers prevent copulation or pollen transfer

• Gametic - male/female gametes die before unite



Behavioral isolation

An Eastern Meadowlark

Eastern meadowlark call eastern meadowlark call

( http://www.naturesongs.com/eam e1.wav

))


A Western Meadowlark

Western meadowlark call western meadowlark call

( http://www.naturesongs.com/w eme1.wav

105


Habitat isolation

106


Behavioral isolation

• Different species of fireflies do not recognize each others' mating signals and, as a result, do not generally interbreed.


Reproductive barriers

Example of thale cress suffering from hybrid necrosis. Left and right are the healthy parents; center is the sick hybrid offspring.

Pup fish-death valley Credit: Image: Kirsten Bomblies


Sympatric speciation

• Two subpopulations become reproductively isolated with in the same geographic area

• Gain adaptive advantages by using different niches

• Could lead to group being isolated

• Wood frog and leopard frog have mating times and calls



Rates of speciation

Two types:

• Gradualism

- nvolves a slow, steady change in a particular line of descent.

• Punctuated equilibriumsudden rapid change with periods of little change

• The fossil record shows that many organisms have indeed changed gradually over time.

• The fossil record reveals periods of relatively rapid change in many groups of organisms



Rapid Evolution After

Equilibrium

– Rapid evolution may occur after a small population becomes isolated from the main population. This small population can evolve faster than the larger one because genetic changes spread more quickly among fewer individuals.

– Rapid evolution may also occur when a small group of organisms migrates to a new environment. That’s what happened with the

114

Rapid Evolution After

Equilibrium

– Mass extinctions open many ecological niches, creating new opportunities for those organisms that survive. Groups of organisms that survive mass extinctions evolve rapidly in the several million years after the extinction.


animations

• http://www.classzone.com/cz/books/bio_0

7/get_chapter_group.htm?cin=4&rg=anim ated_biology&at=animated_biology&var=a nimated_biology
