ANTH 201 Midterm 1

Biological Anthropology

The subfield of anthropology that studies humans as a biological species

Evolution

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

Macroevolution

Changes after many generations (e.g., speciation); evolution of species, genera, families, and other higher classifications; relevant to interpreting the fossil record

Microevolution

Small genetic changes that occur within a species; evolution within populations

Natural Selection

Differential reproductive success based on heritable traits; advantageous traits become more common while disadvantageous traits disappear; reduces genetic variation and can shift allele frequencies

Adaptations

Traits shaped by natural selection that increase survival and reproductive success (fitness)

Conditions for Natural Selection

Variation in a trait; inheritance of the trait; differential reproductive success based on the trait

Charles Darwin (1809–1882)

Naturalist aboard the HMS Beagle; proposed evolution by natural selection in On the Origin of Species (1859)

Darwin’s Five Theories

Species change; evolution is gradual; evolution leads to speciation; all organisms share common ancestry; evolution occurs through natural selection

Darwin’s Three Postulates

Individuals compete for limited resources; individuals vary in fitness-related traits; some variation is heritable

Christian View

All life forms were created by God exactly as they currently exist

Aristotle

Proposed a hierarchy of life from simple to complex with humans at the top

Archbishop James Ussher (1581–1656)

Estimated Earth began on October 23, 4004 B.C.; believed Earth was young

Scientific Revolution

Encouraged experimentation and the scientific method; increased awareness of biological diversity

Carolus Linnaeus (1707–1778)

Father of taxonomy; created binomial nomenclature in Systema Naturae

Erasmus Darwin (1731–1802)

Suggested species evolved from a common ancestor in Zoönomia

Georges Cuvier (1769–1832)

Founder of vertebrate paleontology; established extinction as scientific fact

Jean-Baptiste Lamarck (1744–1829)

Proposed inheritance of acquired characteristics through use and disuse

Thomas Malthus (1766–1834)

Argued populations grow faster than resources, causing competition

Charles Lyell (1797–1875)

Proposed uniformitarianism and argued Earth was very old

Alfred Russel Wallace (1823–1913)

Independently developed natural selection and presented ideas with Darwin

Competition

Organisms compete for limited resources; not all survive to reproduce

Variation

Individuals differ in traits, and some traits improve fitness

Heritable Traits

Traits can be passed from parents to offspring and become more common over generations

Directional Selection

One extreme phenotype is favored, shifting the population average

Stabilizing Selection

Intermediate phenotypes are favored while extremes are selected against

Disruptive Selection

Both extremes are favored over the average, potentially splitting populations

Maladaptive Traits

Traits that reduce fitness

Sexual Selection

Traits that increase mating success despite possible survival disadvantages

Natural Selection vs. Evolution

Natural selection is one mechanism of evolution; selection acts on individuals while evolution occurs in populations

Blending Inheritance

Incorrect theory that offspring traits are averages of parents’ traits, which would eliminate variation

Cell

Basic unit of life containing genetic material and cellular structures

Prokaryotic Cells

Simple single-celled organisms without a nucleus

Eukaryotic Cells

Complex cells with nuclei containing genetic information

Somatic Cells

Body cells forming tissues, organs, bones, and blood

Gametes

Reproductive cells with half the normal genetic material (haploid)

Chromosomes

DNA-containing structures in the nucleus occurring in homologous pairs

Mitosis

Somatic cell division producing identical diploid cells

Meiosis

Cell division producing haploid gametes

Fertilization

Fusion of sperm and egg to form a diploid zygote

DNA

Double-helix molecule storing hereditary information

Base Pairs

Adenine pairs with thymine; cytosine pairs with guanine

Codons

Triplets of DNA bases specifying amino acids

DNA Replication

DNA strands separate and complementary strands are synthesized

Gene

DNA segment coding for a functional product and inherited as a unit

Alleles

Different versions of a gene

DNA Codes For

Proteins and regulatory sequences controlling gene expression

Mutations

Changes in DNA sequence; source of new genetic variation

Recombination (Crossing Over)

Exchange of DNA during meiosis creating new gene combinations

Gregor Mendel (1822–1884)

Established laws of inheritance through pea plant experiments

Law of Segregation

Parents pass one allele for each trait to offspring

Law of Independent Assortment

Genes assort independently during gamete formation

Homozygous

Having identical alleles for a gene

Heterozygous

Having different alleles for a gene

Dominant

Allele expressed when one or two copies are present

Recessive

Allele expressed only when two copies are present

Genotype

Genetic makeup of an organism

Phenotype

Observable characteristics of an organism

Linkage

Genes close together on the same chromosome tend to be inherited together

Co-dominant

Multiple alleles expressed equally

Polygenic Traits

Traits controlled by multiple genes

Pleiotropic Genes

Genes affecting multiple traits

Continuous Variation

Range of intermediate phenotypes often caused by polygenic inheritance

Modern Synthesis

Combination of genetics with Darwinian evolution

Norm of Reaction

Range of phenotypes produced by one genotype under different environments

Environmental Variation

Environmental effects on phenotype expression

Hidden Variation

Genetic variation not normally visible unless conditions change

Gene Flow

Movement of genes between populations introducing variation

Genetic Drift

Random changes in allele frequencies, strongest in small populations

Bottleneck Effect

Loss of variation after a sharp population reduction

Founder Effect

Reduced variation when a new population is established by a few individuals

Evolutionary Constraints

Factors limiting adaptive evolution

Historical Constraints

Evolution limited by a population’s past history

Developmental Constraints

Limits caused by developmental systems and correlated traits

Material Constraints

Physical and chemical laws limiting adaptations

Biological Species Concept (BSC)

Species are groups capable of interbreeding and reproductively isolated from others

Reproductive Isolation

Barriers preventing successful breeding between groups

Ecological Species Concept (ESC)

Species defined by ecological niche rather than reproductive isolation

BSC vs. ESC

BSC emphasizes reproductive isolation; ESC emphasizes ecological differences despite gene flow

Speciation

Formation of new species from ancestral populations

Allopatric Speciation

Speciation caused by geographic isolation

Character Displacement

Competition causes species to diverge morphologically

Reinforcement

Selection against hybrids strengthens reproductive isolation

Parapatric Speciation

Speciation with adjacent populations and limited gene flow

Sympatric Speciation

Speciation without geographic separation

Ecological Niche

The role or “job” of a species in its environment

Adaptive Radiation

Rapid diversification into many species filling different niches

Phylogeny

Evolutionary family tree showing relationships among species

Systematics

Study and construction of evolutionary relationships

Taxonomy

Naming and classification of organisms

Plesiomorphies

Ancestral traits

Apomorphies

Derived traits

Synapomorphies

Shared derived traits used to determine relationships

Cladistics

Classification based on shared derived characteristics

Homologous Structures

Similar structures from common ancestry

Analogous Structures

Similar-function structures without common ancestry

Cladistics Steps

Identify homologous traits; determine primitive vs. derived; compare shared derived traits; choose the most parsimonious tree

Outgroup

Distantly related species used to identify primitive traits

Cladists View

Taxonomy should depend only on descent relationships

Evolutionary Systematists View

Both descent and overall similarity matter in taxonomy