Exam Ii, Chpt. 22-24

Front 1

Biological species concept

Back 1

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

Front 2

BSC shortcomings

Back 2

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

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Morphospecies concept

Back 3

Members of the same species usually look alike

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Shortcomings of the morphospecies concept

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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)

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Ring species

Back 5

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

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Examples of ring species

Back 6

Russian bird population, some plant groups

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Ecological niche

Back 7

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

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Ecological species concept

Back 8

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

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Evolutionary species concept

Back 9

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

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EvSC shortcomings

Back 10

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

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EvSC most useful with...

Back 11

Asexual species

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Most constructive way to think of species

Back 12

BSC

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Pre-zygotic isolation factors

Back 13

Act before the fertilization of the egg

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Examples of pre-zygotic isolation factors

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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

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Lock and key systems

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

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Post-zygotic isolation factors

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

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Example of post-zygotic isolation

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

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Partial reproductive isolation

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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

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Allopatric populations

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Populations that are geographically separated from each other

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Subspecies

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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)

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How do populations become allopatric?

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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)

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Which speciation events are most easily studied?

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

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Example of a vicariance event

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Formation of the Isthmus of Panama, separating marine organisms

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Peripatric speciation

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

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Mainland population

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Central population of a species

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Island population

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

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Adaptive radiation

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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

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Example of adaptive radiation

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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

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Co-speciation

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

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Example of co-speciation

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Parasites and their hosts - lice and pocket gopher

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Sympatric

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Populations that exist in the same geographic location

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Sympatric speciation?

Back 32

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

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Evidence for sympatric speciation

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Plants, fish in the isolated lakes of Cameroon

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Evidence somewhat against sympatric speciation

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

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Instantaneous speciation

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

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Example of instantaneous speciation

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

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Tetraploid

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Plant is double diploid - has four genomes

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Polyploid

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Multiple chromosome sets present

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What chromosome numbers dominate plants?

Back 39

Even numbers

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Must natural selection play a role in speciation?

Back 40

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

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Reinforcement of reproductive isolation

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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

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Phylogeny

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History of descent with branching

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Node

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Indicates last common ancestor of two species that diverged

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Phylogenetic tree

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

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Phylogenetic trees analyze...

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Morphologies and molecular attributes

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Sister groups

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

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Taxonomy

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Formal means of naming groups

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Monophyletic

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

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Paraphyletic

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

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Polyphyletic

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Groups that do not include the last common ancestor

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Order of taxonomic classification

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

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Characters

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

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Reasons why character states may be similar

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

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Homologous characters

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Characters that are similar because of descent from a common ancestor

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Analogous characters

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Characters that evolved independently in the two groups

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Synapomorphies

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

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Cladistics

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Phylogenetic reconstruction on the basis of synapomorphies

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Parsimony

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

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Phylogenetic reconstruction based on synapomorphies

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Nucleotide changes differentiate nodes

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Phylogenetic reconstruction based on distance

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

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Primates

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Prosimians, monkeys, and apes

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Primate distinguishing features

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Nails rather than claws, frontal eyes, opposable thumbs

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The closest relative to humans is...

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The chimpanzee

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Split between humans and chimpanzees occurred...

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5-7 mya

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Hominins

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

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Sahelanthropus tchadensis

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7 million mya, right after human-chimp split

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Ardi

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

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Lucy

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3.2 mya, fully bipedal - Australopithicus afarensis

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Multiregional hypothesis

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

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out-of-Africa hypothesis

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

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Methods used to test both hypotheses

Back 71

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

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Cro-Magnon

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First population of Homo sapiens to arrive to Europe

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Neanderthal interbreeding with Homo sapiens

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

Front 74

Why the discrepancy between mtDNA and full genome?

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