Human Evolution Unit 1

Anthropology

The study of humankind

Subfields of Anthropology

**Cultural Anthropology:** Study of cultures and human societies in the recent past

**Archaeology:** Study of past societies and their cultures

**Linguistic Anthropology:** The study of and evolution of language

**Physical Anthropology:** Study of human evolution and variation

Big Six Events

1. **Bipedality:** (6+ mya) upright walking
2. **Non-Honing Canines:** (5.5 mya) chewing
3. **Material Culture and Tools:** (3.3 mya) use of stone tools
4. **Speech:** (2.5 mya) express complex thoughts and speech
5. **Hunting:** (1 mya) group organizes to pursue animals for food
6. **Domesticated Foods:** (11 kya) farming plants and animals

Domestication

The process of adapting wild plants and animals for human use

Darwin’s Ideas

Natural Selection

Descent with Modification

Lamarckism

Physical changes in organisms during their lifetime (greater development of an organ) could be transmitted to their offspring

Alfred Wallace

**The Wallace Line:** Biogeographic “barrier” that separated Asian origin animals and Australian origin animals for millions of years

Adaptation

Physical or behavioral traits that enhance an organism’s ability to survive and reproduce

Evolution

A change in the allele frequencies of a population over time

Parallel Evolution

When two unrelated organisms evolve a similar trait due to environmental factors

Artificial Selection

Intentional breeding of plants and animals in favor of specific traits which produce offspring with those desired traits

Natural Selection

Process by which some organisms with traits that allow them to adapt to the environment pass on these traits, increasing the frequency in the population

Mutation

Random change in a gene or chromosome making a new trait

Gene Flow

Exchange of alleles between populations of organisms

Genetic Drift

Change in allele frequency from one generation to the next, often due to random events; bigger effect on small population (bottleneck and founder effect)

Homology/Analogy

**Homology:** Structures that are similar in related organisms

**Analogy:**

Gregor Mendel

**Laws of Inheritance**

Bred pea plants, discovered plants had either yellow or green peas, never a mix of colors

DNA

Molecules in all living things that carry specific genetic code; heritable material

RNA

A nucleic acid similar to a single strand of DNA

Genes

Basic unit of inheritance; a sequence of DNA on a chromosome coded to produce a specific protein

Allele

Alternative form of a gene (T or t)

Dominant/Recessive Genes

**Dominant:** T; overrules the recessive

**Recessive:** t; overruled by the dominant

Evidence for Continental Drift

Marsupial fossils on different continents even though they aren’t in these locations today, we can measure the slow drifting of continents, continental land masses fit together like a puzzle

Sexual Selection

The frequency of traits that change due to those traits being preferred to members of the opposite sex (colorful male birds)

Sexual Dimorphism

Body size differential between sex of organisms (males bigger than females)

Eukaryotes

DNA contained in a nucleus; some single-celled and all multicellular organisms

Prokaryotes

Single-celled bacteria; no nucleus or organelles

Endosymbiotic Hypothesis

Free living proteo-bacterium incorporated into the early eukaryotic cell

Forms of Sex Determination

**XY:** Humans; male is XY, female is XX

**ZW:** birds, most reptiles, fish, insects; male is ZZ, female is ZW

**XO:** Some insects, bony fish, arachnids, crustaceans, mollusks; males have XO, females have X

Meiosis

Cell division that leads to haploid sex cells (gametes)

A diploid stem cell divides twice but DNA is only replicated one, so the four end products are haploid (non-identical)

Mitosis

Somatic cell replication and division, forming two identical diploid “daughter cells” (genetically similar to parent)

DNA Replication

Parent strand unwinds

Forms two template strands which display “unpaired” nucleobases (DNA “unzips”)

Pair with respective compliment on the template strand

Two new identical strand are made from one initial strand

DNA Transcription

First step of protein synthesis

A strand of DNA is copied into a new molecule of messenger RNA (mRNA)

DNA Translation

Second step of protein synthesis

Transfer of amino acids by transfer RNA to the ribosomes which are then added to the protein chain

Polygenic Traits

When multiple genes contribute to a single effect

Pleiotropic Traits

When a single gene has multiple biological effects

Epigenetics

Chemical changes in the genome that affect how DNA is used in production of proteins without altering the DNA sequence

Gene Expression

Process in which the gene code is used in the synthesis of a functional gene product

Malaria/Sickle-Cell Anemia/Heterozygote Advantage

Heterozygote in case of malaria and sickle-cell anemia is more evolutionary than either homozygotes

Four Types of Reproductive Isolation

**Geographic Isolation:** Separation of species from mating due to physical barriers in the environment

**Temporal Isolation:** When populations reproduce in different times of the year

**Ecological Isolation:** When populations live in same general area but inhabit different habitats within that are, rarely encounter one another

**Behavioral Isolation:** When two populations of the same/closely related species develop difference in behavior (mating rituals) that leads to divergence

Types of Selection

**Directional:** Selection for one allele over the others, causes shift in allele frequency

**Disruptive:** Selection for both extremes of the phenotype, may lead to speciation event

**Stabilizing:** Selection against the extremes of the phenotypic distribution, decreases genetic diversity

Hardy-Weinberg Equilibrium

Hypothesizes that gene frequencies remain the same because no evolutionary change takes place

Evolutionary “Fitness”

Average number of offspring produced by parents with a particular genotype compared to those with another genotype

Hox Genes

Regulatory genes that determine the form and arrangement of tissues (eye on fly butt)

Microevolution

Small-scale evolution; changes in allele frequency

Macroevolution

Large-scale evolution; speciation event, occurs over hundred of thousands generations