Evolutionary Theory 4

Physical/Biological anthropology

Dates to as far back as the 18th century.

➢ Primary focus was on physical variation among humans

❖ Researchers were dedicated to

measuring bodies and skulls.

➢ Thought it was possible to

differentiate/rank “human biological

races”

There are no biological human races

➢ All humans alive today are members of the same species

The name change is an effort to move away from the outdated term and its association to scientific racism

➢ The new name includes studies that relate to biology and culture amongst human and non-human primates

Biological anthropology contains several subfields:

• Paleoanthropology

➢ Primatology

➢ Bioarchaeology

➢ Genetic anthropology

➢ Forensic anthropology

Taxonomy

The science/technique of naming and classifying life.

Taxon

A group in a taxonomic classification.

➢ Canis (genus) is a taxon

Taxa

The plural form of taxon, used to signify all taxonomic groups.

➢ Canis and Felis together are two taxa

Binomial Nomenclature

The scientific naming system that represents two parts of a taxonomic name.

➢ Assigns two Latin names to each organism

❖ The name is italicized, the genus is always capitalized, and the species is always lowercase

➢ Example: Felis catus (domestic cat)

Species

A class of individuals that have some common characteristics or qualities.

➢ Usually based on behavior, genetics, and/or morphology.

➢ Species definitions are the basis for scientific names

Folk Taxonomy / Ethnotaxonomy

A species’ common name is generally based on physical characteristics by a culture or local population.

➢ Common names are also referred to as folk taxonomy or ethnotaxonomy.

Ethnotaxonomy:

The study of organism classifications and taxonomies developed and used largely by Indigenous peoples and other cultural groups

Four concepts of a species

• Biological species

• Ecological species

• Phylogenetic species

• Recognition species

Biological Species Concept (BSC)

States that a species is a group of interbreeding organisms that are reproductively isolated from other groups of organisms

Reproductive Isolation:

Conditions that prevent potentially

interbreeding populations from breeding

Ecological Species Concept (ESC)

Emphasizes the role of natural selection in maintaining species boundaries.

○ Based on the idea that gene flow is neither necessary nor sufficient to maintain species boundaries

Hybrid Zones:

Areas where two distinct species mate and produce offspring

Phylogenetic Species Concept (PSC)

Defines a species as the smallest group of organisms that share a common ancestor and also exhibit unique traits.

○ The species forms one branch on a phylogenetic tree

Interspecific Variation:

The genetic variation seen between two species

Intraspecific Variation:

The genetic variation seen within a species

Mate Recognition Species Concept

States that a species is a set of organisms that recognize one another as potential mates

The Units of Life

❖ Cells are the basic units of life in all organisms.

❖ Two types of cells; prokaryotes and eukaryotes.

❖ Cell division results in new cells

Genotype

The genetic constitution of an individual organism

Phenotype

Observable characteristics/traits of an organism

Allele

An alternative form of a gene that arises by mutation.

➢ Found in the same place on a chromosome, directly impacting the expression of a genetic trait or phenotype

Law of Segregation:

When two alleles for a trait separate during the formation of new zygotes, these alleles will combine at random with other alleles

Law of Independent Assortment:

Different genes and their alleles are inherited independently

Mendel’s laws of inheritance apply to humans.

➢ Human blood type is a familiar Mendelian trait

❖ A majority of human traits are not controlled by a single pair of genes.

Polygenic traits

Traits that are controlled by multiple genes instead of just one

Evolution

Changes that appear in a species over time.

➢ Evolution is dependent on genetic variation and natural selection to pass on beneficial traits that will increase survival of the species

Before the 19th century, Western

thought emphasized

a fixed natural system

Great Chain of Being:

A concept detailing a hierarchical structure of all matter and life

Inheritance of Acquired Characteristics:

The disproved idea that an organism can pass on to its offspring physical characteristics that it has acquired during its lifetime

Catastrophism:

The theory that changes in Earth’s fauna and flora were caused by supernatural catastrophic forces rather than evolution

Uniformitarianism:

The concept that Earth’s surface was shaped in the past by slow-moving geological processes

Artificial Selection:

The process of deliberately breeding certain specimens of plants or animals to encourage desired traits.

➢ Commonly associated with the process of domestication

An Essay on the Principle of Population (1798)

➢ Human populations, if unrestrained, will grow exponentially

➢ Food resources increase much more slowly than population does

■ Growth of human populations is kept in check by a limit of food resources, which creates a struggle for existence

Natural Selection:

The process by which a species that is able to adapt and to pass on beneficial traits to its offspring ensures survival of the species

Allopatric/Geographic Speciation:

Speciation that occurs when two populations of the same species become isolated from each other due to a change in the environment, such as geographic isolation

5 Theoretical Components of Natural Selection

• All organisms are capable of producing offspring faster than the food supply increases

• All organisms show variation

• There is a fierce struggle for existence, and those with the most suitable variations are most likely to survive and reproduce

• Variations, or traits, are passed onto offspring (inherited)

• Small changes in every generation lead to major changes over long periods of time

Mutation

An alteration in a genetic sequence that results in a variant form

➢ The creative force of evolution

Genetic drift

Random changes in the frequencies of alleles in a gene pool

Gene flow

The exchange of genetic material between populations and geographic regions

Speciation

The rise of a new species in response to an environmental change or pressure

Gradualism

The idea that species evolve slowly and

continuously over long periods of time.

○ Traditional view

Punctuated Equilibrium

A phenomenon of long periods of stasis,

followed by quick periods of change.

○ Suggests that rapid changes due to

environmental factors

Homologous Structures:

Similar anatomical structures that appear in different species and suggest a common ancestor.

Analogous Structures:

Anatomical similarities between two species that suggest not a common ancestor but rather similar environmental adaptations

Cladistics

❖ The classification of organisms based on branchings of descendent lineages from a common ancestor.

➢ A method of visually distinguishing between homologous ancestral and derived characteristics

cladograms

➢ A branching tree diagram that shows ancestral relationships among organisms

Ancestral Characteristics:

Homologous structures or traits that may also be found in the common ancestor of the species being classified

Derived Characteristics:

Physical traits that are present in related organisms but absent from their last common ancestor.

➢ Often associated with a speciation event