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74 Cards in this Set

  • Front
  • Back

Biological species concept

Species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups

BSC shortcomings

Difficult to test in nature, cannot be applied to asexually reproducing organisms, cannot be applied to already extinct populations

Morphospecies concept

Members of the same species usually look alike

Shortcomings of the morphospecies concept

Members of a species may show polymorphisms (color difference in bird species), males may look different from females, young may look different from old, some species may look similar but actually be different genetically (butterflies)

Ring species

Contain populations that are reproductively isolated from each other, but can still exchange genetic material via other linking populations

Examples of ring species

Russian bird population, some plant groups

Ecological niche

A complete description of the role the species plays in its environment - its habitat requirements, its nutritional and water needs, etc

Ecological species concept

The idea that there is a one to one correspondence between a species and its niche, two species cannot exist in the same location if their niches are too similar because competition will lead to extinction

Evolutionary species concept

Members of a species all share a common ancestry and a common fate - all members descended from a common ancestor

EvSC shortcomings

How far should it be applied? All mammals a single species?

EvSC most useful with...

Asexual species

Most constructive way to think of species


Pre-zygotic isolation factors

Act before the fertilization of the egg

Examples of pre-zygotic isolation factors

Behavioral isolation (individuals only mate with other individuals based on specific courtship rituals, songs, and other behaviors), incompatibility between pollen and receiving flower, marine species example (abalone sperm has certain proteins that only will fertilize a female's egg), mechanical incompatibility, temporal separation, ecological separation

Lock and key systems

Systems that require both components, whether physical or biochemical, to match for a successful interaction to take place

Post-zygotic isolation factors

Factors that come into play after fertilization of the egg, usually involve genetic incompatibility

Example of post-zygotic isolation

Two organisms with different chromosome amounts, horse-donkey hybrid (mule) - sterile

Partial reproductive isolation

When two species are not yet totally separate, but genetic differences between them are so extensive that they produce offspring with reduced fertility or viability

Allopatric populations

Populations that are geographically separated from each other


Allopatric populations that have yet to evolve even partial reproductive isolation but which have accumulated a few population-specific traits (Indian and Sri Lankan elephants)

How do populations become allopatric?

Dispersal (some individuals colonize a distant place like an island, far from the main population) or vicariance (a geographical barrier arises within a single population separating it)

Which speciation events are most easily studied?

Vicariance derived speciation - can date the time of speciation as when the vicariance occurred

Example of a vicariance event

Formation of the Isthmus of Panama, separating marine organisms

Peripatric speciation

Type of dispersal, a few individuals from a mainland population disperse to a new location remote from the original population and evolve separately

Mainland population

Central population of a species

Island population

A patch of habitat on the mainland that is appropriate for the species but is geographically remote from the initial mainland population's habitat

Adaptive radiation

A bout of unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adaptation - occurs when there are many ecological opportunities available for exploitation

Example of adaptive radiation

Galapagos finches - arrive on Galapagos islands, no birds on the island to eat the plant seeds - whole array of plant seeds available, no competition, abundance of large and small seeds favored large and small beaks - opposite of stabilizing selection on the mainland


Process in which two groups of organisms speciate in response to each other at the same time

Example of co-speciation

Parasites and their hosts - lice and pocket gopher


Populations that exist in the same geographic location

Sympatric speciation?

Natural selection could act against the offspring of two species, thus isolating the two species and preventing gene flow

Evidence for sympatric speciation

Plants, fish in the isolated lakes of Cameroon

Evidence somewhat against sympatric speciation

Peripatric speciation could have resulted in one species moving into another specie's territory, not sympatric speciation

Instantaneous speciation

Typically occurs with hybridization between two species and the offspring are reproductively isolated from both parents

Example of instantaneous speciation

Two sunflower species, passing on a mix of the parental chromosomes to offspring - chromosome numbers may change in many cases of plant hybridization


Plant is double diploid - has four genomes


Multiple chromosome sets present

What chromosome numbers dominate plants?

Even numbers

Must natural selection play a role in speciation?

Not necessarily - genetic drift, but it does facilitate allopatric speciation and causes sympatric speciation

Reinforcement of reproductive isolation

Process by which diverging populations undergo natural selection in favor of enhanced pre-zygotic isolation to prevent the production of less fit offspring - mating discrimination an example - more commonly induced by natural selection with sympatric species


History of descent with branching


Indicates last common ancestor of two species that diverged

Phylogenetic tree

A hypothesis about the evolutionary history, or the phylogeny, of the species

Phylogenetic trees analyze...

Morphologies and molecular attributes

Sister groups

Groups that are more closely related to each other than either of them is to any other group


Formal means of naming groups


All members share a single common ancestor not shared with any other species or group of species


Includes some but not all of the descendants of a common ancestor (2 cuts necessary)


Groups that do not include the last common ancestor

Order of taxonomic classification

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species


Anatomical, physiological, or molecular features that make up organisms - lungs, etc

Reasons why character states may be similar

Evolved from a common ancestor, independently evolved to similar environmental conditions

Homologous characters

Characters that are similar because of descent from a common ancestor

Analogous characters

Characters that evolved independently in the two groups


Shared derived characters (homologies may not be shared by all members of a group)


Phylogenetic reconstruction on the basis of synapomorphies


Choosing the simpler of two or more hypotheses to account for a given set of observations

Phylogenetic reconstruction based on synapomorphies

Nucleotide changes differentiate nodes

Phylogenetic reconstruction based on distance

Count differences between sequences of different species - greater difference, further apart from common ancestor


Prosimians, monkeys, and apes

Primate distinguishing features

Nails rather than claws, frontal eyes, opposable thumbs

The closest relative to humans is...

The chimpanzee

Split between humans and chimpanzees occurred...

5-7 mya


Members of all the different species in the lineage leading to humans

Sahelanthropus tchadensis

7 million mya, right after human-chimp split


4.4 mya, walked upright, but all four limbs on trees


3.2 mya, fully bipedal - Australopithicus afarensis

Multiregional hypothesis

Implies that Homo sapiens derive from Homo ergaster populations that spread around the world starting 2 mya, all evolving in parallel

out-of-Africa hypothesis

Modern humans arose from Homo ergaster descendants in Africa 200,000 years ago

Methods used to test both hypotheses

mtDNA used, Y chromosome - neither are affected by recombination so they are unaltered over time


First population of Homo sapiens to arrive to Europe

Neanderthal interbreeding with Homo sapiens

It happened as Homo sapiens left Africa, mtDNA suggests otherwise, but whole genome sequencing says that interbreeding did occur

Why the discrepancy between mtDNA and full genome?

Genetic drift resulted in mtDNA lineage loss or only Neanderthal males interbred with Homo sapiens