Unit 1:part 2 (lesson 5+) Flashcards Preview

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Flashcards in Unit 1:part 2 (lesson 5+) Deck (61):
1

speciation

the process by which one species splits into two or more species
-responsible for the diversity of life
-explains differences and similarities between species

2

microevolution

changes over time in allele frequencies in a population

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macroevolution

broad pattern of evolution above the species level

4

biological species concept

says that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring-but do not produce such offspring with other species

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reproductive isolation

the existence of biological factors that impede members of two species from interbreeding and producing viable, fertile offspring
-block gene flow between species
-limit hybrids
-types: prezygotic and postzygotic

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hybrids

offspring that results from the mating of two individuals from different species

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prezygotic barriers

block fertilization from occurring
types: habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation

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postzygotic barriers

prevent a hybrid zygote from developing into viable, fertile adult
types: reduced hybrid viability, reduced hybrid fertility, hybrid breakdown

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habitat isolation

-prezygotic barrier
-two species that occupy different habitats in the same area may encounter each other rarely

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temporal isolation

-prezygotic barrier
-species breed at different times of day, different seasons, or different years

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behavioral isolation

-prezygotic barrier
-courtship rituals that attract mates and other behaviors unique to a species may cause isolation

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mechanical isolation

-prezygotic barrier
-mating is attempted but morphological differences prevent its successful completion

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gametic isolation

-prezygotic barrier
-sperm of one species may not be able to fertilize the eggs of another species

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reduced hybrid viability

-postzygotic barrier
-genes of different parent species may interact in ways that impair the hybrid's development or survival in its environment.

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reduced hybrid fertility

-postzygotic barrier
-hybrids are sterile

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hybrid breakdown

-postzygotic barrier
some first generation hybrids are viable and fertile but their offspring are feeble and sterile.

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limitations of the biological species concept

-can be applied only to a limited number of species
-does not apply to organisms that reproduce asexually
-cannot evaluate fossils
-some species are morphologically and ecologically distinct but have gene flow

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morphological species concept

characterizes a species by body shape and structural features
-distinguishes most species but can be subjective

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ecological species concept

views species in terms of its ecological niche; the sum of how members interact with nonliving and living parts of their environment

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phylogenetic species concept

defines a species as the smallest groups of individuals that share a common ancestor, forming one branch of the tree of life
-compares separate species

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allopatric (other country) speciation

gene flow is interrupted when a population is divided into geographically isolated sub- populations
-once separation has occurred, different mutations arise and natural selection and genetic drift may alter allele frequencies

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Evidence for allopatric speciation

-regions that are isolated or heavily subdivided typically have more species
-reproductive isolation between two populations generally increases as the distance between them increases

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Sympatric (Same Country) Speciation

-speciation that occurs in populations that live in the same geographic area
-can result from polyploidy, habitat differentiation, or sexual selection

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polyploidy

an accident during cell division that results in an extra set of chromosomes;
may allow a new species to originate
-most common in plants
-can result from non-disjunction

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autopolyploid

an individual that has more than two chromosomes sets that are all derived from a single species

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allopolyploid

has 2 or more chromosome sets as a result of 2 different species interbreeding
-can mate with each other but not parent species

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habitat differentiation

genetic factors enable a sub-population to exploit a habitat or resource not used by the parent population

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non-disjunction

when homologous chromosomes do not separate during meiosis, sex cell will contain too few or too many chromosomes

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hybrid zone

a region in which members of different species meet and mate, producing at least some offspring of mixed ancestry
-form when 2 species lacking complete barriers to reproduction come into contact

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reinforcement

strengthening of reproductive barriers
-can occur when hybrids are less fit than parent species

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fusion

weakening reproductive barriers
-much gene flow occurs between two species, gene pools become increasingly alike and eventually fuse into a single species

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Stability

continued formation of hybrid individuals
-sometimes hybrids are fitter
-sometimes hybrids are at disadvantage but a small hybrid zone with migration might occur

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punctuated equilibria

In the fossil record, long periods of apparent stasis in which species undergo little or no morphological change interrupted by relatively brief periods of rapid speciation

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Speciation Rates

-experiments and observations suggests that once the process of speciation begins, it can be completed rapidly
-on average, millions of years may pass before a newly formed species will give rise to another species

35

plate tectonics

continents are part of great plates on Earth's crusts that essentially float on the mantle
-plates move over time

36

Consequences of Continental Drift

-alters habitats in which organisms live
-causes climate changes as continents shift location: organisms adapt, move, or become extinct
-promotes allopatric speciation (continents break apart)
-helps explain geographic distribution of extinct organisms.

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Pangaea

supercontinent formed about 250 million years ago
-destroyed shallow water habitats, interior cold and dry
-caused extinction, new opportunities for surviving species

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Mass Extinction

time in which large numbers of species became extinct

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Permian Mass Extinction

-between paleozoic and mesozoic eras
-claimed 96% of marine species and many insect species
-enormous volcanic eruptions in Serbia 251 million years ago
-warmed atmosphere, oxygen levels dropped

40

Cretaceous mass extinction

-between Mesozoic and Cenozoic eras
-about 65.5. million years ago
-50% of marine species and many terrestrial plants and animals extinguished
-hypothesized to have been caused by an asteroid striking the earth

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Consequences of Mass Extinctions-

-reduces diversity of life
-changes types of organisms found in ecological communities
-can end lineages with highly advantageous features
-paves way for adaptive radiations

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Adaptive Radiations

periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities
-often occur after mass extinctions
-organisms increase in diversity as they play new roles in the environment
-organisms that arise can serve as new food source

43

taxonomy

the scientific discipline of naming and classifying organisms

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binomial nomenclature

names organisms using two part name
-genus name+ specific epithet

45

Hierarchical Classification

Domain
Kingdom
Phyla
Class
Order
Family
Genus
Species

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phylogenetic tree

a branching diagram that represents a hypothesis about the evolutionary history of a group of organisms
1. Intended to show pattern of descent, not phenotypic similarity
2. Sequence of branching in a tree does not necessarily indicate the actual age of a species
3. Do not assume that a taxon evolved from a taxon next to it

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PhyloCode

a system of classification that only names groups that include a common ancestor and all of its descendents

48

rooted

describes a phylogenetic tree that has a branch point that represents the most recent common ancestor of all taxa

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polytomy

a branch point from which more than 2 descendent groups emerge
-signifies evolutionary relationships among taxa not yet clear

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homoplasies

analogous structures that arose independently

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molecular systematics

the discipline that uses data from DNA and other molecules to determine evolutionary relationships

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cladistics

an approach to systematics that uses common ancestry as the primary criterion to classify organisms

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clades

groups that include an ancestral species and all of its descendents

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monophyletic

a group that consists of an ancestral species and all of its descendants

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paraphyletic

consists of ancestral species and some of its descendents

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polyphyletic

includes new taxa with different ancestors

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shared ancestral characters

a character that originated in an ancestor of the taxon

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shared derived characters

an evolutionary novelty unique to a clade

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outgroup

a species or group of species from an evolutionary lineage that is known to have diverged before the lineage that includes the group we are studying

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maximum parsimony

the principle that systematists should first investigate the simplest explanation that is consistent with all of the facts
- requires fewest evolutionary events, or fewest DNA base changes

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maximum likelihood

given certain probability rules about how DNA sequences change over time, a tree can be found that reflects the most likely sequence of evolutionary events