Darwin's theory of evolution by natural selection · 2.2 Give support for your thesis ... brain, bone, and muscle Sex cells (gametes) - unites with another gamete from each ... double-stranded

Darwin's theory of evolution by natural selection

Week 3

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Announcements

-HW 1 - will be on chapters 1 and 2 DUE: 2-27

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Summary

*Essay talk

*Explaining evolutionary change

*Getting to know natural selection

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*Immediately get to the point-don't start with a cheesy opener like "Webster's dictionary defines gene as…"

-Capitalizing: names of the fields are lower case:

"...cultural anthropology, archaeology, physical anthropology,..."

Tautologies

It's Genus species = Homo sapiens

Common annoyances . . .

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1. Introduction1.1 Introduce the main subject of the essay1.2 State your thesis1.3 Briefly detail how the rest of the essay addresses/supports your thesis

2. Body of the essay - supporting your thesis (number of paragraphs varies with the differing questions)

2.1 Background or introduce the topic in detail (one paragraph)2.2 Give support for your thesis2.3 Give more support OR address potential objections to your thesis or support for the thesis

3. Conclusion3.1 RESTATE thesis

3.1.1 BRIEFLY recap/remind the reader that you've supported your thesis (in the body of the essay).

3.2 . . .

Solid essay outline

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-Every new generation has more offspring born than can survive (1)-There's constant competition for resources (2)-There's biodiversity among individuals in a generation (3)

If all three of these circumstances are evident, then "favorable variations would tend to be preserved, and unfavorable ones to be destroyed. The result would be the formation of a new species" (Origin of Species)

Key observations influencing Darwin

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(i) Individuals in a population vary in inherited traits

(ii) Some individuals are more fit, i.e., they have higher reproductive success because they have advantageous traits

(iii) Selective pressures (environment, predation, etc) determine which traits are advantageous

(iv) Over time, the proportion of individuals with advantageous traits increase while the proportion of individuals without such traits decreases

Required conditions for natural selection to occur

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Fitness: a measure of relative reproductive success of individuals-measured by an individual's genetic contribution to the next generation compared to other individuals

Reproductive success: number of offspring an individual produces and rears to reproductive age

Selective pressure: forces in the environment that influence reproductive success in individuals-what causes distinct species to develop

Important terms for evolution by natural selection

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Artificial selection-All domestic dogs share a common ancestry-There's extreme variation exhibited by dog breeds due to artificial selection

Natural selection in detail - analog with artificial selection

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(i) traits must be inherited if natural selection is to act on it (ii) natural selection cannot occur without population variation in inherited traits(iii) fitness is a relative measure that changes as the environment changes(iv) natural selection only acts on traits that affect reproduction


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(i) natural selection only acts on heritable traits

(ii) natural selection cannot occur without population variation in inherited traits

(iii) fitness is a relative measure that changes as the environment changes

(iv) natural selection only acts on traits that affect reproduction


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8. Geographical isolation contributes to formation of new species as individuals adapt to different environments and respond to different selective pressuresInfluenced by observations and Wallace's biogeography

Natural selection in detail - Eight processes

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Q: How could you turn a pack of wolves into Chihuahuas?

Note: All dogs descended from wolves

If you're given a pack of wolves to breed, how would you start breeding the wolves to eventually make a Chihuahua?

Example 1: Dog breeding

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1. Think about the question

2. Discuss question in pairs

3. Share answers to whole class

Exercise 2: Peacock trains

Q: How would you test whether peacocks with large spots on their trains have 'good genes'?

NS example exercises

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Competing hypothesis: Intelligent Design

-many criticisms but here are the three best criticisms

1. (quick) We can't differentiate between designed things and naturally occurring things. Which every rock in this picture is naturally formed except the 500th from the right in the bottom row.

2. Intelligent design is so vague it fails as a design inference

3. ID is a terrible explanation and outclassed by evolutionary theory

Competing hypotheses and social controversies about evolution

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1. (quick) We can't differentiate between designed things and naturally occurring things. Which every rock in this picture is naturally formed except the 500th from the right in the bottom row.




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1. (quick) We can't differentiate between designed things and naturally occurring things. Every rock in this picture is naturally formed except the 5th from the right in the bottom row.


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What's a good design inference then?

Design inferences are based on our background experience with human intentions

Intentions: goals, aims, and desires a person has

Examples

1. Pug, chicken, grizzly bear, camel spider

-It's obvious the first two are the products of human design because we have background experience with humans designing animals for pets


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Examples

2. Arrowhead, fishing hook, etc - our background knowledge that humans design tools to hunt allows archaeologists to infer design in arrowheads and other artifacts found at archaeology digs


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Examples

2. Arrowhead, fishing hook, etc - our background knowledge that humans design tools to hunt allows archaeologists to infer design in arrowheads and other artifacts found at archaeology digs


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Good explanations have the following characteristics

*Disconfirmable - there can be evidence against it

*Testable - the explanation makes predictions that (i) we can test scientifically and (ii) past the tests

*Background knowledge - the explanation is consistent with facts independent of those it is trying to explain


Genes, DNA, cells and the biological basis for life

Week 4

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1. There needs to be variation among the individuals of a population for natural selection to act

Constraint: Darwin was unable to explain why there's variation seen among populations

2. Adaptations (favorable traits) are inherited from parent to offspring

Constraint: Darwin was unable to explain how the process of inheritance works

Constraints on the 19th century version of natural selection

GeneticsGenetics studies gene structure and action

Genetic mechanisms undergird evolutionary change

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Cells - General CompositionOrganelles - substructures in the cell performing various functionsE.g., protein synthesis, energy storage, waste disposal, etc.

Nucleus - contains DNA and RNA

Ribosomes - organelles in part made up of RNA; involved in protein synthesis

Mitochondria - powerhouse of the cell - produces energy; think: cell's engines; also has DNA: mtDNA

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Cells - Two typesSomatic cells - body tissues e.g., organs, brain, bone, and muscle

Sex cells (gametes) - unites with another gamete from each parent which forms a zygote. They transmit genetic information from parents to offspring.

Zygote - Potential to develop into a new organism, contains all the chromosomes (46 for us)

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ProteinsFunction - attach to various molecules to perform different functions

Hemoglobin (Hb) - binds w/ oxygen and transports it around the body

Collagen - (tissue composition) - most common protein in the body

Enzymes - regulate chemical reactions; E.g., digestive enzyme lactase breaks down lactose into simpler sugars.

Hormones - affect different tissues and organs. E.g., Insulin made by specialized pancreas cells causes the absorption of glucose in liver cells

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DNADNA (deoxyribonucleic acid) - Double-stranded host of the genetic code

RNA (ribonucleic acid) - single-stranded molecule messenger (mRNA)transfer (tRNA)

DNA + RNA contain the genetic information controlling the cell's functions

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DNAStructure-nucleotides stacked on top of each other form the double-stranded twisted ladder-like structure

Nucleotides: composed of a sugar, a phosphate (sides), and a nitrogenous base (rungs)

Bases - form complementary bonds

Adenine bonds with Thymine

Guanine bonds with Cytosine30

Protein SynthesisDNA determines the structure and function of proteins

Proteins: made of chains of amino acids

Function is determined by the number and arrangement of amino acids making up the chain

Amino acids - building blocks of proteins

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Darwin's theory of evolution by natural selection · 2.2 Give support for your thesis ... brain, bone, and muscle Sex cells (gametes) - unites with another gamete from each ... double-stranded