ANT 201: Intro To Evolutionary Theory

Introduction to Evolutionary Theory

Evolution

Change in trait frequencies time

• Specifically allele frequencies

-> at its core evolution is a genetic process

Ex: if flies change eye color from one generation to the next it is considered evolution

MICRO vs. MACRO

Evolution on a small scale New species are created

• Evolutionary theory is focused on change through time and the diversification of life

Theory = an explanation for natural phenomena, thoroughly tested and supported

Fact = an observable phenomenon

• Evolution—> It is BOTH a theory and a fact

Brief History of Evolutionary Thought:

Aristotle Great Chain of Being; Fixity of species

- species didn't change

St. Augustine of Hippo Creation of Earth and “Types” of Life

- types could change

Ibn Khaldun Humans evolved from the primates

- Humans are the highest

Thomas Malthus Resources affect population growth

- famine, floods etc.

Georges Cuvier Used anatomy to study extinction

- Paleontology

Charles Lyell Uniformitarianism

- a geological process that takes time (the earth was old enough)

Transmutation Hypothesis:

Living species are derived from older; similar species

Jean-Baptist Lamarck’s inheritance of acquired characteristics

• Changes you made individually would be passed on

use/disuse affects structures and heritability of traits

Ex: neck length of giraffes

This is NOT TRUE (this is not how traits are passed on)

Evolution via Natural Selection:

• Variation exists and is heritable

• Competition exists because there are limited resources

• Differential survival and reproduction (fitness)

• Beneficial traits to increase its frequency

Evolution occurs at the Population or Species level

Pop = group of individuals from the same species

• Individuals can’t evolve during their lifetime

• Natural selection does not lead to the development of new traits → mutation does

• Creation and evolution can be inherently compatible

(often on an individual approach)

Ancestral Traits V.S Derived Traits

• Large group - Small group

Social Darwinism: If you are in a certain condition ( poverty, jail) it is because you are genetically disposed to be in that setting → WRONG

Stabilizing Selection: Extremes are selected against

Directional Selection: Selection against one extreme [one direction]

Ex: moth colors pre + during Industrial revolution

Diversifying(disrupting) Selection: selection for the two extremes of trait

08/31/23

Cell Structures and Functions

Basic Structure + Function of Cells

• Membrane (regulates the passage of molecules)

• Cytoplasm (jelly-like matrix holds organelles)

• Nucleus (contains cell’s DNA)

• Mitochondrion (produces adenosine triphosphate)

• Endoplasmic (synthesis of proteins, lipids, carbohydrates)

• Ribosomes (Protein synthesis)

• Centrioles (assist cell division)

Procaryotes: single-celled Eukaryotic: single or multi-celled

DNA Structure

Sugar + Phosphate+ Nitrogen base= Nucleotide

[backbone] [4 bases ATCG]

• Nitrogen Bases: adenine- thymine, cytosine- guanine [AT] + [CG]

• A single strand of DNA will contain this equation

• The two strands of DNA are considered complementary and antiparallel + connected by complimentary base pairs

• Approx. 3 million base pairs in a single cell

• Two types of DNA: DNA in the nucleus (codes for all process + protein)

Mitochondria DNA [MT]

• Nuclear DNA is DNA that is passed down by both parents whereas mitochondria DNA is only inherited from the female

DNA Replication

• Initiation: ENnzyme comes in and separates hydrogen bonds that keep the complementary strands together

• Elongation: Enzyme (DNA preliminary) reads the order that is on each separate strand and brings their complementary bases

• Considered semi-conservative

(composed of some of the original strand and one new strand)

• Termination: Completion and creation of nucleotide

Protein Synthesis

• Another nucleic acid is RNA

(DNA is the other)

• Single-stranded

• Lacks thymine and is replaced with uracil [CG] + [AU]

• Important for protein synthesis

1. Two DNA strands are partially separated

• Only partially to read the proteins

1. RNA preliminary comes in and reads one strand for protein and brings its complimentary bases

Creates a pre-mRNA + undergoes splicing

- mRNA → messenger RNA

• Some of the code is cut out (intron) to connect exons

• Alternative Splicing= different combinations of exons lead to different proteins

1. Translation: mRNA goes to the ribosome and is read in 3 based sequences k known as codons

• Transfer TRNA is going to have to have the opposite codons

• As it is reading the amino acids link to create a peptide chain

Chromosomes

DNA -> Chromatin -> Chromosome

Chromatin = tightly coiled

Euchromatin = loosely coiled

• Nucleolus tightly wraps around histones, tightens up more, and forms a chromatin fiber which becomes even tighter and forms a a chromosome

Chromosome structure:

Center: centromere

Ends: Telomere

Arms: short (p) + Long (q)

• On one chromosome we have genes

• Genes are coding sections of DNA found on a chromosome

-structural + regulatory

• Alleles are alternate forms of a gene

* Someone doesn’t necessarily have good genes they have good alleles (makes distinct features)

• Locus: the region of a chromosome where a particular gene is located

• Genome: the entire set of DNA in a cell

Somatic Cells

• Humans have 46 chromosomes (23 homologous pairs)

- one: mom one: dad

• 22 autosomal pairs, 1 pair of sex chromosomes

• Diploid (two of each type of chromosome)

XX: female Xy: Male

• Trysomine 21 = down syndrome

• Any other mutation before 21 will likely lead to a miscarriage

• Homologous chromosomes share the same allele for a particular gene = homozygous

Different allele = heterozygous

• Dominant: an allele that is always expressed [CAPATALIZED]

• Recessive: allele that is expressed when there are two copies [lowercase]

• Genotype: the combination of alleles present

• If the dominant allele is present that is what will be expressed

• Homozygous Dominant : AA

• Homozygous Recessive: aa

• Heterozygous: Aa

• Phenotype: physical traut expressed based on the genotype

Gametes

• Humans have 23 chromones

+ 23 autosomal

Cell Division

Mitosis:

1. Start with a diploid cell

2. DNA Replication → copies of chromosome remain joined as sister chromatids

3. Chromosomes line up in the senter→ chromatids attach to spindle fibers

4. Sister Chromatids are then pulled apart

5. End with two diploid daughter cells, each identical to the parent cell

Meiosis:

1. Start with the diploid parent cell

2. Chromosomes replicated, form sister chromatids

3. Homologous chromosomes come together

4. Crossing over (recombination) Spindle fibers attach

5. Cell divides into 2 cells

6. End with 4 haploid daughter cells/gametes

- Final step only happens if fertilization occurs and only 1 of the 4 is taken

( only have 1 chromosome cell so it can be combined during fertilization)

Which of these processes is the most important from an evolutionary standpoint?

Answer: Meiosis

Because it is involved in the reproductive process

• What is the difference between mitosis and meiosis?