Anthropology Exam 1 Study

What is a theory?

Theory is a broad, natural explanation for a wide range of phenomena, Theories are concise, coherent, systematic, predictive, and broadly applicable, often integrating and generalizing many hypotheses

What is Evolution?

change over time, Change in allele frequencies from one generation to the next

What is Natural Selection?

The process whereby any heritable features that enhance fitness of an organism, relative to its peers, increase in frequency in the population in succeeding generations.

Natural Selection Clarification Language:

• Variation: differences between individuals

• Inheritance: encoded in DNA, trait passed to offspring

• Selection: environmental pressure

• Competition for resources

• Time: but not too much!

• Adaptation: change in phenotype

What is Evolutionary Theory?

• Fitness = ability to survive and reproduce; reproductive success

Scala Natura or Great Chain of Being

Gods at top, human males, elephants, dolphins, then human females, emphasized linear thinking, no change over time

Al-jahiz, muslim zoologist

• Individuals of the same species struggle against each other and stronger, more adapted species prevail with lesser mortality rates, Environmental conditions were a driving factor in organisms, and they developed new traits to survive in their environments.

AI-Beruni (Iranian Polymath)

Humans ‘migrated’ through the ‘kingdoms’ of minerals, plants, and animals in order to reach perfection and contains within himself the nature of the creatures of the realms, • Monkeys were the creature that humans had migrated from, before becoming human

Pre-1600s Europe

Literal interpretation of the bible, Earth believed to be a few thousand years old, “created” around 4000 BC according to some estimates

Fixity of Species (Pre-1600s Europe)

all life on earth created by God perfectly and exactly as it presently existed and did not change

1600s and 1700s

Scientific revolution, Galileo’s ideas eventually became more accepted, netwon’s laws of physics, Linnaeus

Linnaeus (1707-1778)

Father of Taxonomy, Established systme of binomial nomemclature (Genus, species), Added class and order, placed humans with other primates

Linnaean Classification

Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Primates

• Family: Hominidae

• Genus: Homo

• Species: sapiens

Buffon (Evolutionary Theory) 1700s

• Noted that different geographical regions had slightly different looking plants and animals, despite similar habitats, Environment could change species, but not create new species. Idea that species are not completely static; they may change and the environment may drive that change

Eramus Darwin

proposed the idea that species could change over time due to environmental changes, Idea that living species descended from common ancestors,

Lamarck (Evolutionary Theory)

Inheritance of acquired characteristics, theory of “Use” or “Disuse”, provided a mechanism for evolution. Traits acquired by an animal during its lifetime can be passed on to its offspring

George Cuvier

Catastrophism – the earth is shaped by sudden events that altered life (e.g. floods) (WRONG)

He noticed several points in the rock record where evidence of life would stop suddenly and then abruptly reappear

Charles Lyell

• Wanted geology to be a objective science, • Same geologic processes that influence the earth today, influence the earth a long time ago – the earth is OLD, studied under a catastrophist who was linked geology to the bible, did not agree with it.

Uniformitarianism

An example is the grand canyon, We can measure how much erosion takes place/year through wind, running water, etc. •Relatively small amount in absolute terms •If these processes go on for many years, the cumulative effect of even small changes adds up to really big changes

Thomas Malthus

An essay on the principle of population, populations increase faster than food supplies, competition for resources

Alexander von Humboldt

Father of biogeography

Charles Darwin

Inerested in natural science & geology, at 22 (1831) invited aboard the HMS Beagle as a naturalist (5 year voyage) He built off concepts from Lyell (geogoly and Malthus (economics)

Darwin’s mechanism for evolution

All species are capable of producing offspring at a faster rate than food supplies increase

• All living this exhibit variation

• Due to limited resources, there is competition between individuals, a “struggle for existence”

• Individuals with traits allowing them to survive in a particular environment will have an advantage over others

• Favorable traits are passed on to future generations

LAMARCK

DARWIN

Alfred Russel Wallace

Also came up with the theory of evolution by natural selection, Caused Darwin to publish On the Origin early • Extensive work in Amazon & Malay Archipelago

Natural Selction derived from three facts - the 3 postulates of natural selciton

1) More offspring are produced than the food supply can support (creates competition)

2) There is variation among individuals within all species

3) This variation is heritable

Erasmus Darwin Idea of Ancestors

All livng things have a common ancestor

What are adaptations?

• Traits that interact with the environment to help an organism survive and reproduce • Adaptations lead to the appearance of organisms being well-suited, or well-designed, to their environment

How does natural selection work to produce adaptations

traits that can be passed down allow organisms to adapt to the environment better than other organisms of the same species. This enables better survival and reproduction compared with other members of the species, leading to evolution.

Directional Selection

Selection for a particular trait which shifts the population in one direction or another…. E.g. shallower or deeper beaks (on average)

Disruptive Selection

selection away from the average condition and towards extremes in both directions

Stabilizing Selection

selection to maintain the equilibrium state centered around the average

Balancing Selection

Heterozygous advantage with sickle cell and malaria – Aa don’t get malaria

Evolution: other mechanisms

• Notice that evolution by natural selection is a non-random process that is adaptive, • Change in environment and origin of variation may be random, but evolution by natural selection is not.

Evolution can also happen randomly:

Genetic Drift

Founder Effect

Mutation

• Continuous variation

height, beak depth, etc, • Things that are measurable in terms of height, length, depth, etc.

Discontinuous variation

presence/absence of certain features, drastic color differences, etc (Qualitative differences…can’t directly measure • You either have wings or you don’t • There are red males and blue males)

Convergent Evolution

When species evolve similar traits independently (not because of recent shared common ancestor that also had those traits)

Anagenesis

gradual change in one lineage over time….no branching speciation event

Stasis

no change in a lineage over time…population is in equilibrium or stabilizing selection

Cladogenesis

division of a single lineage into two lineages; a branching event

Phyletic gradualism

gradual change in the morphology of a population of organisms through time, either anagenetic or cladogenetic or both

Punctuated equilibrium

morphology of most species is in equilibrium for long periods of time, punctuated by rapid morphological and genetic shifts that result in the formation of new species • Stasis interrupted by rapid speciation events

Eukaryotic Cells

Complex cells with a nucleus, more complex than simple prokaryotic cells, evolved ~1.2 billion years ago, eukaryotic cells are found in all living multicellular organisms.

What surronds the nucleus?

Cytoplasm, it contains numerous organelles, Organelles involved in cell activities such as breaking down nutrients, storing and releasing energy, getting rid of waste, and manufacturing proteins

What process are proteins manufactured?

Protein Synthesis

Ribosomes

organelles that play a major role in protein synthesis

Mitochondria

organelles that play a major role in energy production within the cell, Have their own DNA (mtDNA) which direct mitochondrial activities

Chromosome

structure of supercoiled DNA in nucleus

Centromere

center of chromosome

Chromatid

each individual arm of chromosome

Sister chromatids contain what?

exact copies of the same genetic material

How many pairs of chromosomes do humans have?

23 pairs, one inherited from mom, other from dad. Homologous chromosomes are NOT exact copies.

How many TOTAL chromosomes in human somatic cells (nonsex cells)

46 total, but yes 23 pairs.

23 is the human ____ number

haploid

46 is the human ____ number

diploid

Somatic Cells

most cells in body (e.g. liver, heart, brain) has 46 chromosomes (diploid)

Sex Cells (gametes)

sperm or egg cells, 23 (haploid)

Mitosis

occurs in somatic cells, one diploid cell divides into 2 diploid cells.

Meiosis

occurs to form gametes (sex cells), one cell divides into 2 cells, then those 2 cells divide again into 4 cells.

Mitosis starts and ends with…

starts with 1 diploid cell (46) ends with 2 diploid cells (46), continous process throughout lifetime of individual

Meiosis starts and ends with…

starts with 1 diploid cell (46) ends with 4 haploid cells (23) crossing over or recombination occurs during Prophase 1, process happens only at specfic times throughout life.

DNA =

“backbone” of sugar and phosphate molecules • Attached to the sugar is one of 4 “bases

4 Bases (DNA)

Adenine = A

Thymine = T

Guanine = G

Cytosine = C

DNA nucleotide

subunit of DNA that contains one sugar, one phosphate and one nitrogenous base.

DNA Repilcation

DNA parent molecule splits and duplicates to create two identical daughter helices. • This occurs before cells divide (mitosis/meiosis) • Sometimes errors occur in this process which are called mutations

What is a Gene?

Region of DNA that codes for a specific protein. • Basic unit of heredity in a living organism.

Protein Coding Genes

Code for enzymes, which control the chemical composition of cells by promoting some chemical reactions but not others • Proteins other than enzymes are also involved in many vital cellular functions • Provide structure (keratin, collagen) • Regulate many cell activities • Convey chemical signals (insulin)

Transcription

DNA sequence is copied to messenger RNA molecule

Translation

RNA is translated into an amino acid chain (or protein)

DNA FACTS

• double stranded • never leaves nucleus • bases are A, C, G, T • deoxyribose sugar backbone

RNA FACTS

• single stranded • leaves nucleus • bases are A, C, G, U • ribose sugar backbone

What were Mendel’s experiments?

• Identified pea plants characters (traits) with only 2 states/conditions: Through selective breeding, Mendel created “true” strains of plants containing each character state • E.g., plants that only produced green peas every generation • Mendel then performed many crosses between true breeding plants • E.g., green pea plants crossed with yellow pea plants

Genotype

The combination of two versions of a gene (called alleles) that a person has inherited, genetic makeup of an individual, Can refer to a single locus OR more broadly an individuals entire genetic complement

Phenotype

Individual’s observable traits - Physical (observable) expression of an organisms genotype

Allele

Alternative versions of one gene

Simple traits

Traits whose variations are controlled by different versions of a single gene, Mendel’s traits are Simple Traits

Chromosomes (Mendels Experiments)

Discrete structures found in all cells • Made of coiled DNA

Locus (loci=plural)

Location of a gene on a chromosome

In Mendel’s Garden:

- Variants of genes at single locus are called alleles - Follow distribution of alleles across generations - Use laws of probability to compute how alleles will be distributed

Mendel’s inferred…

Each individual inherits 2 alleles, one from each parent •. Mendel called alleles “particles.” • When dominant alleles are present, they “mask” some traits • Recessive phenotype is not expressed → Mendel’s first law of inheritance: Dominance.

Some alleles are:

dominant and are always expressed • recessive and are never expressive in the presence of a dominant allele • codominant and are both expressed if both are present

Inheritance Patterns

Each gamete received one gene copy/allele • Traits (e.g., pea color) are determined jointly by 2 gene copies/alleles, 1 inherited from mother and 1 from father → Mendel’s second law of inheritance: Segregation

Meiosis and Segregation

Each gamete receives one allele

• Homozygous

having the same allele at the same locus on both chromosomes TT or tt

Heterozygous

: having different alleles at the same locus Tt

Alleles of two or more genes…

get sorted into gametes independently of each other e.g., seed texture and color sort independently → Mendel’s third law of inheritance: Independent Assortment

1)Law of Dominance

Offspring have expression of the dominant allele

2)Law of Segregation

Each gamete receives just one gene copy, which is selected randomly

3) Law of Independent Assortment

Alleles of two (or more) different genes get sorted independently of one another

Genes on the same chromosome recombine

Crossing over/recombination occurs • During meiosis, part of one chromosome is replaced by the same segment on a homologous chromosome • The closer together two loci are, the more likely they are to stay together and get passed on together

Simple Traits

Traits whose variations are controlled by different versions of a single gene

• Complex traits

Traits that are influenced by more than one gene (polygenic) or environmental factor

Evolution

is defined as a change in allele frequencies within a population from one generation to the next

Population Genetics

The study of how genes (alleles) evolve in populations, The study of allele frequency distribution and change under the influence of four evolutionary forces

Best known force of evolution

Natural selection (Gene flow, mutation, genetic drift)

Hardy-Weinberg Equation

Equation that was developed to determine the frequency of two alleles at one locus in a population, Mathematical model which we compare null prediction against actual observed data • If a population is in “Hardy-Weinberg Equilibrium” then evolution has NOT occurred

Hardy-Weinberg Equation (ALLELES)

• Mutation is NOT occurring

• Population is infinitely large

• Natural Selection is NOT occurring

• Mating is random

• No migration in or out of the population

Natural Selection allele frequencies

• If one phenotype is associated with higher fitness (i.e., greater ability to survive and reproduce), then alleles that result in that phenotype will increase in the population • Evolution by natural selection at the genetic level