Evolution

Chapters 16 and 17

• Why should we study evolution?

• What exactly is evolution?

To help you build a solid foundation to answer this question here is a very brief history…

• Initially, Europeans believed Earth was only a few _________________ years old

• New evidence indicating an older Earth began to accumulate, especially in the new field of ________________

• James ___________ and Charles __________ put together geologic evidence showing that– the Earth was not a few thousand years old

but much ____________– the rate in the past was the ________ as it is

now.

The true concept of deep time is unimaginable for most people.

We will look at this more later.

____________ and Population Growth• If a ___________________ is unchecked,

eventually, there would not be enough living space or food for everyone

Evidence was accumulating that species change over time.

But how do species change over time?

_____________’s Evolutionary Hypotheses

• Organisms could change during their lifetimes by selectively using (or not using) various parts of their bodies

• Organisms want to ____________ and _____________ so they do (acquired traits)… This makes them more successful

• Individuals could pass these acquired traits on to their _________________, enabling species to change over time

What was wrong with ______________’s Evolutionary Hypotheses?

• Organisms do not have an inborn drive to ____________ ________ ____________

• ______________ __________: traits that ____________ be passed on to offspring–Ex. Tailless rats, plants grown in various

altitudes

What was wrong with Lamarck’s Evolutionary Hypotheses? (cont.)

• Evolution does not mean that over time a species becomes “____________”

• Evolution does ______ progress in a ______________________ path– Environments change and species either adapt

to survive in their environments or _____ _____–A trait that works well for one

______________________ might not work so well in another

Charles Darwin• Charles Darwin studied all of these ideas• He also studied ______________ ______________• He knew that–Many ___________ vary within a species–Variations in ________ are selected for or against

when _______________ plants and animals• Darwin applied this idea to all _________________,

not just ________________ organisms

Darwin Traveled Around the World

Darwin’s First Observation During His Travels

• Species ________ ____________: different animal species that have the same niche (job) inhabited separated, but ecologically similar, habitats around the world.• Example:

S. America’s Rhea

Africa’s OstrichAustralia’s Emu

Darwin’s Second Observation During His Travels

• Species ________ ____________: different, yet related, animal species often occupy different habitats within a local area.

• Ex. Galapagos Island tortoises and mockingbirds, two species of rheas in South America

Abingdon Island tortoiseVolcán Wolf tortoise

Chatham Island tortoiseSierra Negra tortoise

Darwin’s Third Observation During His Travels

• Species ________ ________ _______: some fossils of extinct animals were similar to living species.

• Ex. armadillos and glyptodont

Darwin’s Conclusions:

• If more individuals are born than can ____________ individuals must compete for limited ____________

• Darwin called this the “_______________ ______ __________________”

_______________ ____ ___________

Darwin’s Conclusions:___________

• Individuals naturally have variation of their ________________ traits within a species

• ________ variations increase or decrease an individual’s ability to survive

Darwin’s Conclusions:_____________

• _________________: Any heritable characteristic that increases an organism’s ability to survive and __________________ in its environment

• ____________________ can involve– body parts or structures (claws, thumbs, tails)– colors (camouflage, mimicry)– physiological functions (digesting certain foods,

photosynthesis)– behaviors (not moving when danger is near, hearding)

• Adaptation occurs over ________________ ______ in an individual lifetime (acclamation)

Darwin’s Conclusions:_________ __ ___ ________

• ____________: How well an organism can survive and __________________ in its environment

• This ________ ______ mean the biggest/strongest/healthiest/fastest/etcetera organisms survive.

• This means the individual that passes their genes on to the most _______________. Examples?– Sneaker male cuttlefish Video– Sneaker male tree frog Video

Darwin’s Conclusions:_______ _________

• ____________ _______________: Is the process by which organisms with variations most suited to their local ____________________ survive and leave more ________________

• The environment, not humans, influences ________• In order for natural selection to occur ______ things

must happen…

Natural Selection1. More ___________ are born than

can _______2. There is natural _______ variation3. There is a variable _______ among

individuals4. Competition for limited _________

Darwin’s Conclusions:________ ________

• Over long __________ (deep) time and through environmental variations successful ___________ evolve into new ____________

• If you go far enough back all organisms are ___________

Principle of ______ _______: all species both living and extinct are descended

from ______ ancestors

Evidence of Evolution• Biogeography• Fossil Record• Anatomy• Cellular and Molecular• Analogous Structures & Imperfections• Testing Natural Selection

• The distribution of many species does not make sense, unless they shared a _____________ ancestor.

• If species were unchanging, then you would expect to find the ________ species in areas with ___________ environmental conditions around the world.

• Evolutionary theory, however, predicts that modern species should be found _________ to where their _________________ were, regardless of the environmental conditions.

• This is the major type of evidence that convinced Darwin.

____________Evidence of Evolution:

• Evolutionary theory predicts that islands that have similar ___________________, but are in different parts of the world, will ______ be populated with the same species.

• Instead, these islands should be populated with plant and animal species that are closely related to the species on the ____________ _____________, even if the environment there is very different from the island.

Galapagos Iguana Green Iguana

• The _____________________ order of the major groups seen in the fossil record shows a succession of species that is predicted by evolutionary theory

• The ___________ ___________ shows transitions between groups, which are evidence that these groups have a ______________ history

________ ________Evidence of Evolution:

• Example:– ______ appear before amphibians, which appear before

reptiles, which appear before ______________– Mammals are thought to have evolved from a reptilian

ancestor, and this transition is thoroughly documented with a series of fossil _________ (reptiles ->mammal-like reptiles -> reptile-like mammals -> mammals).

– _________________ between fossils and modern species (two exceptionally well-documented cases include horses and humans).

– Whale fossil with ________ __________ is a link between modern whales and their hypothesized terrestrial ancestor

_______ _______Evidence of Evolution:

Evolutionary theory predicts that different species will evolve different forms of shared (________________) traits.• _______________ structure: when two traits are

similar, regardless of the function of the trait• _____________ structure: are structures that are

currently of little use to the organism (i.e. they have no known current function). They are the historical remnants of structures that did have a function in earlier ancestors, and provide evidence for shared __________________.

Evidence of Evolution: _________

Evidence of Evolution: __________ (cont.)

• Examples of ___________________ structure– All vertebrate embryos look very similar during

the earlier stages of development, including having gill pouches and tails

– Tetrapod limbs and bones– Plant leaves modified for various functions– Hind limb bones that baleen whales & snakes

don’t use (Homologous & Vestigial)–Goosebumps (Homologous & Vestigial)– Ear muscles in humans (Homologous & Vestigial)

__________ and ___________• The genetic code is ________________—all plants,

animals, fungi, bacteria, and protists use the same genetic code.

• All organisms are made of ________, which consist of membranes filled with water containing genetic material, proteins, lipids, carbohydrates, salts and other substances.

• The cells of most living things use _________ for fuel while producing ______________ as building blocks and messengers.

Evidence of Evolution:

• Many of the ______________ reactions occurring in your own cells, in the cells of a fungus, and in a bacterial cell are quite different from one another; however, many of them are exactly the same and rely on the exact same molecules. ______ is one such molecule; it is essential for powering cellular processes and is used by all modern life.

Evidence of Evolution:__________ and ___________

• Examples:– the similarity between the typical animal and

plant— only ______ structures are unique to one or the other

–Roundworms, for example, share 25% of their genes with humans.

__________ _________ & _____________• Evolutionary theory predicts that different organisms will

independently evolve similar solutions to the same functional problem (analogy).

• ______________ structure: when a trait in two different species is similar and they have the same function

• Analogies are the result of _________________ evolution• ______________ Evolution: Process in which two distinct

lineages evolve a similar characteristic ______________ of one another.

• Evolutionary theory predicts that some traits will not be “perfectly” adapted

Evidence of Evolution:

• Example of __________________ Structures– the wings of bats, birds, and insects all serve the

same basic function (flight) and are similar in appearance. They are not similar because of shared ancestry (the common ancestor of bats, birds and insects did not have wings). Bat wings consist of flaps of skin stretched between the bones of the fingers and arm. Bird wings consist of feathers extending all along the arm.

• Example of ____________________– Giant panda’s “thumb”, a modified wrist bone– Hiccups: The first air-breathing fish and amphibians

extracted oxygen using gills when in the water and primitive lungs when on land—and to do so, they had to be able to close the entryway to the lungs, when underwater. In hiccupping, we use ancient muscles to quickly close the glottis while sucking in. One of the reasons it is so difficult to stop hiccupping is that the entire process is controlled by a part of our brain that evolved long before consciousness

Evidence of Evolution:__________ _________ & _____________

_________ _______ ____________• ______________ selection provides a model

for ________________ selection– People have been artificially selecting

domesticated plants and animals for thousands of years.

– These activities have amounted to large, long-term, practical experiments that clearly demonstrate that species can change dramatically through selective breeding.

Evidence of Evolution:

• Experiments demonstrate selection and adaptive advantage– Colorful guppies vs drab guppies– Cholera

Evidence of Evolution:

Male guppy

Female guppy

_________ _______ ____________

• We can see nested hierarchies in taxonomies based on common descent– Groups of related organisms share suites of similar

characteristics and the number of shared traits increases with relatedness

Evidence of Evolution:_________ _______ ____________

Evolution of Populations

• Does evolution work on genotype or phenotype?– _______________ because it is the whole organism

that survives and reproduces… or does not

Evolution of Populations:__________ of ___________

• __________________• Recombination in Sexual Reproduction:

Crossing over during meiosis

Evolution of Populations:__________ _______ Traits

• The number of phenotypes is determined by the number of genes that control the trait

• __________ ________ Trait: usually 2-3 phenotypes

• Homozygous recessive or dominant usually results in two different phenotypes

• Heterozygous might result in third phenotype

Evolution of Populations:__________ _______ Traits

If an allele is dominant(over a recessive allele)

does that mean that it is more common in the population? Why?

Evolution of Populations:___________ _______ Traits (cont.)

______• Natural Selection works on the ________ of the

individual regardless of if the trait is dominant or recessive. This affects the whole population.

Kitten with 23 toes

White forelockPolydactyl

Uncommon Dominant Traits Common Recessive Hair straight & red; eyes blue

• ______________ Traits: Trait controlled by 2+ genes with 2 or more alleles each. Usually results in a range of the _________________

Evolution of Populations:________________ Traits

• ____________________ Selection: One extreme is selected for (or against)

• _________________ Selection: Both extremes are selected against so the middle is selected for

• _________________ Selection: Both extremes are selected for and the middle is selected against

Evolution of Populations:How does evolution affect _______ Traits?

_________

_________

_________

• __________________: random changes in allele frequency caused by a series of chance occurrences that cause an allele to become more or less common in a population

Evolution of Populations:____________ _________

• ___________ ______: a change in allele frequency followed by a major reduction in the size of a _________________

Evolution of Populations:_________ ______ (a type of genetic drift)

• ______________ ____________: a few individuals become isolated from the larger population. These individuals reproduce within this secluded group _________________ the initial genetic diversity

Evolution of Populations:Founder Effect (a type of genetic drift)

Veiled chameleon on Hawaii

What conditions cause evolution to occur in a balanced system?

• ___________________ ________________– This is an active selection for or against a trait

What conditions cause evolution to occur in a balanced system?

• __________ population size– Changes in individuals of a _________ population

can quickly spread to the whole population

What conditions cause evolution to occur in a balanced system?

• ________________ or ____________________– A change in the amount of alleles or the

arrival/departure of alleles

Haemochromatosis is caused by one specific mutation in the HFE gene, located on chromosome 6. In Australia, all patients can actually be traced back to one single

immigrant carrying the mutation.

What conditions cause evolution to occur in a balanced system?

• _______________: A change in the genetic material

What conditions cause evolution to occur in a balanced system?

• ____________ __________: The process by which organism that are most suited to their environment survive and reproduce most successfully; A.K.A survival of the fittest