ANTH 201 Midterm 1 - UofC

ANTH 201 (Winter 2025) - UofC

LECTURE 1: INTRO & EVOLUTIONARY THOUGHT

1

What is Evolution?

A change in the inherited characteristics of biological populations over successive generations

What is microevolution?

small genetic changes that occur within a species

What is macroevolution?

changes after many generations (e.g. speciation)

Pre-Darwinian Western World View (2)

• Stasis

• Earth is Young

Stasis (2)

• all life forms were created by God exactly as they exist in the present (Christianity)

• all life forms can be placed in a hierarchy from simple to complex with humans at the top (Aristotle)

Earth is Young (figure + date)

Archbishop James Ussher (1581-1656) analyzed Genesis and estimated that the earth began Sunday, October 23rd, 4004 B.C.

The Scientific Revolution

Exposure to new plants and animals increased awareness of biological diversity

Erasmus Darwin (1731-1802)

• Species have evolved from a common ancestor

• Darwins grandfather

Georges Cuvier (1769-1832)

• Ends the debate about whether extinction could occur using fossil evidence (begins the long and ongoing study of the Earth’s fossil record)

Jean-Baptiste Lamarck (1744-1829) (2)

• Inheritance of acquired characteristics (acquired changes are passed onto offspring)

• Lacked mechanism (genetic proof)

Thomas Malthus (1766-1834) (2)

• Populations grow exponentially in times of plenty, but eventually are checked by famines, disease, etc.

• There will be competition to survive

Charles Lyell (1797-1875) (2)

• Developed principle of Uniformitarianism (geological/physical laws of today are directly influenced from the past)

• Indicated Earth was very old

Alfred Russel Wallace (1823-1913)

• Independently developed idea of natural selection

LECTURE 2: NATURAL SELECTION

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What were key points in Darwin’s book, Origin of Species? (2)

• Species can change

• Species evolve from other species through the mechanism of natural selection

From the 3 postulates, individuals compete because __________

resources are finite

From the 3 postulates, individuals vary in ways that affect ___________

their ability to survive (Ii.e. fitness)

From the 3 postulates, some variation is ________

heritable

Competition (3)

• Populations can expand indefinitely, but resources are always finite

• Individuals compete for limited resources (e.g. food) within a particular habitat

• Not all individuals survive long enough to reproduce

Variation (3)

• There is variation among individuals in a population

• Some individuals will possess traits that make them more successful (i.e. higher fitness)

• Those traits allow them to survive and reproduce, or produce more offspring

Traits are Heritable (3)

• Differences among individuals are transferred from parents to offspring

• Those advantageous will become more common in successive generations

• In Darwin’s time, didn’t understand how traits were passed on to offspring (mechanisms of inheritance still

unknown)

Those traits that help individuals to survive and reproduce are called ___________

Adaptation

Adaptation (ANTH 201 Definition)

a trait that is shaped by natural selection and allows the individual to survive and reproduce more successfully (i.e. increases fitness)

Directional Selection

Favours one extreme trait over the other (i.e. faster cheetahs survive, speed increases in offspring over time)

Stabilizing Selection

Favours the average over the extremes, equilibrium (i.e. human birth weight; too fat or too skinny have lower survivability)

Disruptive Selection

Favours both extremes over the average (i.e. birds with very large or very small beaks survive better than birds with medium-sized beaks)

Misunderstandings about evolution & natural selection (4)

• Natural selection can’t explain the evolution of complex traits

• The unit of selection

• All traits are adaptive

• Evolution is not ‘progress’

Misunderstanding Explained: Evolution of Complex Traits (2)

• Living gastropod mollusks illustrate all of the intermediate steps between a simple eye cup and a camera-type lens

• Demonstrates each “step” can be an important adaptation

Evolution of Complex Traits (3)

• Complex adaptations don’t evolve all at once

• Each change, building on previous small changes, can produce complex adaptations

• “Tinkering” instead of “engineering”

Complex Traits: Convergence

• Unrelated species evolve similar traits due to similar environments and pressures

  Example: Sharks (fish) & dolphins (mammals) both have streamlined bodies for swimming

Misunderstanding Explained: The unit of selection (2)

• Natural selection occurs at the level of the individual (i.e. a bird with a large beak will survive)

• Evolution occurs at the level of the population (changes in gene frequencies, i.e. beak size change over time)

Misunderstanding Explained: All traits are adaptive (3)

• Not all traits count as adaptations

• It’s only an ‘adaptation’ if it contributes to fitness

• Some traits are former adaptations (i.e. the human appendix), and some are just traits (i.e. human chin)

Misunderstanding Explained: Evolution is not a ‘progress’ (2)

• Evolution does not always progress in one direction

• ONLY better suited to a particular environment (if environment changes, adaptation may be negligible)

Why were Darwin’s theories not accepted at the time? (2)

• Could not explain how variation was maintained

• Could not explain how traits were passed down – the mechanism of inheritance

Drought reduced seed availability, favoring finches with

deeper beaks

Step-by-Step Evolution of the Eye (5 steps)

Light-sensitive cells → Eye pits → Deeper eye cups → Lenses → Fully functional eye

In what circumstance can evolution be ‘fast’ (a few generations or thousands of years)?

When selective pressures are strong

LECTURE 3: CELLS & DNA

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Blending Inheritance

The hereditary substance of both parents is “mixed” or “blended”

Why couldn’t blending inheritance be the mechanism of inheritance?

Blending inheritance dilutes and eventually eliminates variation

The Cell (3)

• Basic unit of life

• Generic material and other structures

• ~ 1 trillion cells in adult human

Prokaryotic Cells (3)

• Initial type of cell (3.7 BYA)

• Single-celled organisms (bacteria & blue-green algae)

• No nucleus

Eukaryotic Cells (3)

• Share common ancestor with prokaryotes

• Complex (1.2-2.1 BYA)

• Have nucleus

Chromosomes (3)

• Small linear bodies contained in cell nucleus

• Replicated during cell division

• Exist in homologous pairs in diploid (2n) organisms

Chromosomes in Humans (2)

• 23 pairs (n), 46 total (2n)

• Two copies of each chromosome (maternal & paternal)

Mitosis (3)

• Normal cell division

• Creates two exact copies of chromosome pairs (diploid)

• Part of normal growth in the body

Meiosis (2)

• Cell division for producing gametes

• Creates single chromosomes, haploid (n) gamete

What happens during fertilization?

Sperms (n) fertilizes ovum (n)

Following fertilization, what is created?

Zygote (2n)

Zygote divides through _____ to build up new organism

mitosis

Chromosomes contain two complex molecules, which are? (2)

• Proteins (histones)

• Nucleic Acids (DNA, RNA)

DNA backbone composition

Phosphate and sugar

Inner links between DNA strands are pairs of nucleotides (bases), which are? (4)

• Adenine (A)

• Guanine (G)

• Cytosine (C)

• Thymine (T)

To which bases do each nucleotides bond? (2)

• A ← → T

• G → ← C

DNA is excellent for _____ information

storing

Gene (2)

• Segment of DNA that makes a functional product and segregates as a unit during gamete formation

• Unit of heredity

Locus

Location on the chromosome where a gene is found

Alleles

Multiples variants of a gene

Differences in DNA Sequence that may cause variation: (2)

• Some DNA codes for proteins

• Some DNA codes for regulatory sequences

Protein-Coding Genes (2)

• Enzymes

• Non-enzymatic proteins

Enzymes

Enzymes catalyze (facilitate) chemical reactions in cells, going from one compound to another involved in the structure and function of those cells

Non-enzymatic proteins

Proteins that are not involved in enzymatic reactions, but play a role in the normal structure and function of cells

Codons (2)

• 3 letter base pairs

• Specify amino acids

What do redundant codons protect against?

Deleterious changes in protein structure caused by DNA damage

Synonymous substitution

One base is replaces by another, but it does not change the amino acid for it

Introns

Non-coding sequence in DNA that is removed

Exons

Coding sequence in DNA, spliced together

The same DNA sequence can code for _______________

multiple proteins

Alternative Splicing

• exons from the same gene are joined in different combinations (increases variation)

• 80% of human genes are alternatively spliced

Operators (2)

• Determine if & when other protein-coding sequences are expressed

• Non-coding but near protein-coding sequence

Binding site: Repressor

Proteins that bind to these sites and block the gene from being expressed (like turning off a light switch)

Binding site: Activator

Proteins that bind and help turn the gene on, allowing it to be expressed (like flipping a light switch on)

Regulatory sequences are a large source of:

phenotypic variation

Gene regulation allows for _____________ from single-cell zygote

Cell differentiation (process where cells specialize into different types with unique functions)

Differential Regulation

Some genes are active in one cell type but inactive in another, leading to variation in function and structure

Mutations

Change in DNA sequence

Point Mutation

change in a single DNA base

Mutations are not always ________

negative (source of variation)

Recombination/Crossing-over (2)

• New combinations of alleles through breaking and rejoining of DNA strands into a new order

• Meiosis, between homologous chromosomes

LECTURE 4: MENDELIAN GENETICS

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Dominant

Variant of gene that suppresses other variants

Recessive

Genes only expressed when there are two copies of the corresponding allele

Mendel’s Law of Segregation (2)

• Alleles account for variation in inherited characteristics

• Organism inherits one gene from each parent, and only passes one on

Mendel’s Law of Independent Assortment (2)

• Each gene separates independently of each other during meiosis

• Emergence of one trait will not affect the likelihood of the emergence of another trait

Homozygous

Both copies of allele are identical

Heterozygous

One dominant allele and one recessive allele

Genotype

Combination of alleles an organism carries (i.e. Aa)

Phenotype

the observable characteristics of an individual (i.e. black fur)

Key Observations from Mendel’s Pea Experiments (3)

• Traits are preserved

• No blending

• Rare traits reappear in later generations

Particulate Inheritance

Traits are determined by discrete particles (genes) passed intact from parents to offspring

What is the expected F2 ratio of a monohybrid cross? (2)

• Genotypic Ratio: 1:2:1 (AA:Aa:aa)

• Phenotypic Ratio: 3:1 (dominant:recessive)

What is the expected phenotypic F2 ratio of a dihybrid cross?

9:3:3:1

Genetic Linkage

If two or more genes are on the same chromosome, they are usually inherited together (unless crossing over happens)

Linkage ______ the rate of recombination

reduces

Why do identical twins have different fingerprints?

because position in womb impacts finger growth rates in 3rd trimester

How is ABO blood type inherited? (4)

A and B alleles are dominant over O

• AA or AO → A blood type

• BB or BO → B blood type

• OO → O blood type

• A and B alleles are co-dominant (AB blood type)

Why is human eye color more complex than Mendelian traits?

Controlled by multiple genes, mainly OCA2 and HERC2 on Chromosome 15

Same genotypes can result in different phenotypes depending on _______________

Development and environment

LECTURE 5: MODERN SYNTHESIS

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