Evolution Review What evidence was there in the early fossil record that species were not immutable?

o Specific fossils found in similar layers around the globe o Fossils of sea creatures found high on mountains o Fossils of creatures that no longer existed on the planet were found

(less than 1% are still alive)o Fossils illustrated an increasing diversity and complexity of life on the

planet over time

What evidence was there to suggest that the Earth was not immutable?

o The continents looked like they fit togethero The same rock formations on 2 different continents o The same fossils in the sock formations on 2 different continents

Baron Georges Cuvier (1769 – 1832)

o Investigated fossils, found that there were layers that contained different species

o Species were unique to that layer. Shell found in one layer couldn’t be found in another.

o Suggested that catastrophes (changes in earth), caused extinctions

o Then another form migrated later on

o Theory of Catastrophism: how species are extinct due to a catastrophe, then species from the surrounding environment will repopulate the area.

Sir Charles Lyell (1797 – 1875)

o Supported Hutton’s theory with the Theory of uniformitarianism

o Said that the earth’s surface is always changing and continues to change.

o supported with fossil samples

o Impact of Lyell and Hutton: Earth is very old, and changes are slow and become dramatic over time.

George Buffon (1707 – 1788)

o Said species change over time into new species

o Introduced idea about common ancestry and similarities between species

Jean-Baptiste Lamarck (1744 – 1829)

o Said species adapt to changing environment, and has some role in evolution

o Theory of Inheritance of Acquired Traits: said that a muscle man would give birth to a muscle baby; from which he was wrong

o Traits from a mother with some influence could pass onto the child

o But that doesn’t mean a full evolution and mutation

o Giraffe elongated neck a bit, and with further exercise after each generation, it might make it grow longer; Theory of I.A.T was proven wrong

Explain Darwin’s Theory of Evolution by Natural Selection and describe the requirements necessary for it to occur.

By definition natural selection is any characteristic of an individual that allows it to survive to produce more offspring will eventually appear in every individual of the species simply because those members will have more offspring.

Requirements;

o Individuals within a species very in many ways

o Some of this variability is heritable(passed on from parents to offspring)

o Every generation produces more offspring that can survive

o Populations of species tend to remain stable in size (due to environmental constraints such as food, predation, disease, etc)

What evidence, other than in fossils, support the idea of evolution of species? (Think about the presentation on whales and other cetaceans…)

Comparative Anatomy

o placenta- give birth to live young

o feed babies milk

o warm blooded

o no gills- 2 fully developed lungs

o blowholes- which spilt into 2 passages like nostrils on the skull

o hair

o arm, wrist, hand, and finger bones in their front flippers

o mysterious pair of bones where back legs should be

Embryology

o similar features in the embryo

Give examples of artificial selection and breeding, and explain how these show evolution of populations. How do populations shaped by artificial selection differ from those shaped by natural selection?

Rats (for temperament so they can be kept as pets), silver foxes (part of an experiment to breed for temperament), cows (some are bred for milk, some for meat), chickens (some grow at twice the rate of normal chickens, although part of that is the fat and antibiotics they're stuffed full of), pigs (for size), also dogs

If you use artificial selection, you are 'favoring' certain traits to be reproduced. If this is done consistently, the individuals with the favored traits will outnumber the individuals with unfavorable traits. Eventually, those individuals will die out, and only the favored traits will remain in the gene pool

Explain the difference (with examples) of the following patterns of selection (from environmental pressure) that we see in populations; stabilizing, disruptive, directional.

Stabilizing

o most common form of selection

o occurs when environmental conditions are relatively stable

o individuals that are near the average for a particular trait are favoured

o extreme phenotypes are rare because of energetic or fitness tradeoffs

o e.g. birth weight in humans – most babies weigh just slightly more than 3 kg, higher morality if under this weight and birth complications if over this weight

Directional

o individuals with extreme phenotypes are favoured

o occurs after the migration of a population to a new environment or after an environmental change

o e.g. climate change and increased flooding of coastal areas may favour more salt-tolerant phenotypes of a specific tree species than those of average salt-tolerance

Disruptive

o individuals with phenotypes at opposite extremes of the range are favoured over those with average phenotypes

o often occurs in response to multiple food sources that require different forms of a trait

o e.g. small and large bills are favoured over medium-sized bills in the black-bellied seedcracker finch in response to 2 different sizes of seeds being readily available

o disruptive selection often results in the division of a species into 2 distinct forms and eventually 2 distinct species

Explain why sexual selection occurs (with examples)? Give examples found in the animal kingdom (including in humans), and explain how sexual selection in your examples would represent an advantage for a female choosing a mate.

o Individuals with traits that make them more likely to breed successfully and produce more offspring are favoured

o Include sexual dimorphism (difference in size) and behavioural differences between sexes

o Most common types result from female mate choice, and from male-versus-male competition for mates

o Examples of traits resulting from female mate choice; decoration of ‘bowers’ by satin bower birds, bright colouration and plumage (feathers) in males of many species, such as the red wing blackbird and peacock, songs in songbird (generally the males are much more vocal)

o Examples of traits resulting from male-versus-male competition for mates; antlers and horns in deer, moose, long-horn sheep, extreme size of male seal elephants, larger size and strength of human males

How do males maximize their evolutionary fitness? Describe several examples.

o Mating with many different females

o Colourful plumage

o The ability to dance and learn different dances (birds)

o The ability to mimic different sounds of the forest and have different songs

Explain how sexual selection often results in sexual dimorphism (males and females having different shapes and appearances) and give examples.

Competition in mate choice leads to selection for mates with preferred characteristics. Baboon males, for example, are highly intolerant of one another and aggressively compete for access to female mates; simply, success in fights results in greater access to females. For this and other dimorphic primates, sexual selection is only one explanation for high levels of dimorphism [e.g. in body size], and may not be the best one. However, new analyses indicate associations between dimorphism and competition levels: where dimorphism is high, male-male competition is commonplace; conversely, where dimorphism is low, competition among males is less frequent.

How do random changes in allele frequencies shape the evolution of small populations?

We can determine how much populations are evolving based upon the frequencies of various alleles (forms of genes) in the population. For instance, if 80% of a population of newts had the red-eyed allele for eye colour at one point in time, but 87% of the same population possessed this allele many generations later, it indicates that evolution has occurred. In other words, evolution can be defined as a change in the frequency of alleles in a population over time.

Though natural selection is always shaping populations, random events often also have a major impact upon the allele frequencies of populations, particularly in small populations. There are three main types of these random events:

1. Genetic Drift:

Genetic drift is the change in the genetic makeup of a population resulting from chance events;

In very small populations, alleles are often lost, resulting in lower genetic diversity (higher homozygosity) and increased likelihood of a catastrophic die-off from a disease outbreak;

Two specific types of genetic drift include:

1. Bottleneck Effect: the result of a severe restriction in population size

small sample of population then has to repopulation

therefore allele frequencies are likely different than original population

often results in lack of genetic diversity (e.g. northern elephant seals)

2. Founder Effect: the result of the movement of a small sample of a population to a new place to start a new population

small sample of population repopulates

likely to bring different allele frequencies in sample

therefore the frequencies of rare alleles may be much higher in the new populations

e.g. allele for abnormally short arms and polydactyly (extra digits) in Amish community of Pennsylvania (started from a founding group of 30 individuals) is 7% compared to 0.1% in original Swiss population

2. Gene Flow:

The movement of organisms from one population to a new population;

Brings new alleles to populations;

Occurs through migration, mating between nearby populations (e.g. in prairie dogs and meerkats), and seed dispersal;

Reduces genetic variation between populations, but doesn’t increase homozygosity (e.g. human travel and mating around the globe is resulting in populations that are less distinct from each other).

3. Mutation:

Mutation is the process by which new alleles are formed:

o occur when DNA is damaged (e.g. from UV light),

o is copied incorrectly, or

o when chromosomes break and are not repaired properly;

o Only have evolutionary significance if they occur in gametes.

What is the Hardy-Weinburg Principle? How can it be used to show the evolution of populations?

The Hardy–Weinberg principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.

What requirements are necessary for a population to be in H-W Equilibrium (i.e. for the H-W Principle to be valid)?

o The population must be very large in size.

o It must be isolated from other populations. (no gene flow)

o No mutations.

o Random mating.

o No natural selection.

Describe each of the different reproductive isolating mechanisms with examples for each type.

Reproductive barriers can be classified into two categories, prezygotic barriers and postzygotic barriers. Prezygotic barriers includes mating between two species which results in the inability to fertilize. Whereas, postzygotic barriers prevent the zygote from developing into a viable adult, should fertilization between two different species occur.

Prezygotic barriers: 1) Ecological isolation - two species that occupy different habitats within the same area may encounter each other rarely, if at all. Example.. The mountain bluebird lives at high elevations, while the eastern bluebird prefers lower elevations and does not encounter the mountain species

2) Temporal isolation - species that breed during different times of the day, different seasons, or different years cannot mate. Example… pussy willows produce flowers in

the early spring. They are reproductively isolated from plant species that produces flowers at a different time of year

3) Behavioral isolation - certain behavioral patterns that attract mates or that are unique to a particular species are effective reproductive barriers. Example… Male frogs of different species have unique calls that attract only females of their own species

4) Mechanical isolation - morphological differences can prevent successful mating. Example… Male damselflies transfer sperm during an unusual mating flight. The male and female genitalia of each species are uniquely shaped and are physically incompatible with other species

5) Gametic isolation - sperm of one species may not be able to fertilize the eggs of another species. Certain biochemical processes may prevent sperm from penetrating the egg of another species, or, the sperm may fail to survive in the reproductive tract of females of another species. Example… Many marine animals including corals, clams, and sea cucumbers release their sperm and eggs into open water. The sperm recognize eggs of their own species through chemical markers on the surface of the eggs.

Postzygotic barriers: 1) Reduced hybrid viability - the interaction of genes between members of two different species may hinder the ability of the hybrid to develop into a viable adult. Example… when tigers and leopards are crossed, the zygote begins to develop but the pregnancy ends in a miscarriage or stillborn offspring.

2) Reduced hybrid fertility - if members of two different species produce viable offspring, the offspring may be sterile. This example is best illustrated by a mule, the hybrid offspring of donkey and horse. Example… Mules are the sterile hybrid offspring of a horse-donkey cross.

3) Zygotic mortality- mating and fertilization are possible, but genetic differences result in a zygote that is unable to develop properly. Example… some species of sheep and goat are unable to mate, but the zygote is not viable.

What is the difference between allopatric and sympatric speciation?

Allopatric speciation means that speciation occurred in different regions. The key with allopatric speciation is geographical separation. Sympatric speciation means that one population of one species became two species while in the same geographic region with no physical separation. This usually occurs because different individuals of the same species begin to occupy a distinct niche and eventually become specifically adapted for that role.

Explain the difference between; divergent evolution, convergent evolution, adaptive evolution, and co-evolution, and give examples of these.

Adaptive Radiation- the relatively rapid evolution of a single species into many new species, filling a variety of formerly empty ecological niches. Example is Darwin’s finches.

Co-evolution- a process in which one species evolves in response to the evolution of another species. Example… the Brazil nut has developed a shell so hard that the agouti is the only mammal with strong enough teeth and jaw to crack the shell.

Convergent Evolution- the evolution of similar traits in distantly related species. Example… similar body shapes of sharks and dolphins

Divergent Evolution- the large scale evolution of a group into many different forms. Examples… Ontario has over 20 species of closely related rodents.

Describe several possibilities for the formation of the first life on Earth.

o Natural selection o Abiogenesis- origin of life from non-living matter

Explain the difference between the theories of gradualism and punctuated equilibrium. Give examples of when these processes have happened in evolutionary history.

Gradualism- states that as a new species evolves, they appear very similar to the original species and only gradually become more distinctive. Ex- evolution of horses

Punctuated Equilibrium- suggests that the process of evolution is slow, but is occasionally punctuated by periods of rapid change Ex- the evolution of shells (which can be argued for both)

What was the Cambrian explosion?

Was the relatively short evolutionary event, beginning around 542 million years ago in the Cambrian Period, during which most major animal phyla appeared, as indicated by the fossil record.

What role has extinction played in evolution? List several major extinction events in evolutionary history.

Extinction leads to open ecological niches which need to be filled by the evolving animals.

1. The Ordovician-Silurian extinction (marine animals- due to low sea levels

2. The Late Devonian extinction (warm marine animals- cause unknown)

3. The Permian-Triassic extinction (95% of all species- worst mass extinction- scientists believe it was a comet or asteroid)

4. The End Triassic extinction (caused by massive floods of lava- lead to the separation of Pangea)

5. The Cretaceous-Tertiary extinction (dinosaurs- thought to be caused by several asteroids)

What are transitional forms? Explain the significance of Archaeopteryx, Aetiocetus, and Tiktaalik.

Transitional forms is a fossil or species intermediate/in-between in form between 2 other species in a direct line of descent

Archaeopteryx- transitional form between reptiles and birds

Aetiocetus- is the transitional form between modern whales and their ancestors.

Tiktaalik- transitional form between fish and land vertebrates

Compare the following groups; primates, anthropoids, hominoids, and hominids.

Primates- are a relatively small group of mammals characterized by large brains relative to body size, forward-directed eyes, flexible hands and feet, and arms that can fully rotate. Examples, monkeys, apes, and humans.

Anthropoids- splits into 2 distinct groups: the monkeys and the hominoids, or apes

Hominoids- includes humans, their fossil ancestors and apes.

Hominids- all species descended from the most recent common ancestor of chimpanzees and humans that are on the human side of the lineage.

What critical adaptations allowed hominids to become so different than their hominoid (i.e. chimp) cousins? (Think skeleton, brain, culture, social)

o Walk upright (bipedal)

o Larger brain relative to size

o Hands are capable of fine manipulation and coordination

o Ability to perform complex reasoning, coupled with an exceptional ability to learn, to make and use sophisticated tools, and to communicate using complex language