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Flashcards in Speciation Deck (73):
1

Large scale biological evolution

The descent of different species from a common ancestor over many generations

2

Population

Members of a species that live in the same geological area and share a common gene pool

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Gene pool

The total number of alleles that occurs in a population

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Deme

A local population that has no or limited gene flow with members of other populations

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Cline

When a species has an extended geographical range and variation occurs along a gradient from one point of the range to another point

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Phylogenetic trees

Evolutionary trees drawn as branching diagrams

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Species

It is a group of individuals that can reproduce (interbreed) to produce fertile offspring

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Allopatric speciation

Physical barriers/geological isolation such as mountain ranges, desert, bodies of water (live in different geographic locations)
Prevents two or more groups from mating with each other causing gene flow to be reduced but not completely

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Sympatric speciation

Where species share the same habitat/live in the same geographic location and one species gives rise to two or more species without any periods of geographical isolation.
Interbreeding is prevented by various biological factors called isolating mechanisms

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What are Prezygotic isolating mechanisms

Act before fertilisation and prevent zygote formation

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What are Postzygotic isolating mechanisms

Act after fertilisation and zygote formation

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Two types of reproductive isolating mechanisms

Allopatric
Sympatric

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Barriers to gene flow that prevent interbreeding

Allopatric
Sympatric

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Examples of selection pressures

Temperature, mutations, mating, birth, gene flow, natural selection, weather, predators, wind exposure

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Prezygotic isolating mechanisms

Temporal isolation
Gamete isolation
Behavioural isolation
Mechanical/structural isolation
Ecological
Geographical

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Temporal isolation

Individuals from different species do not mate because they are active during different times of the day or in different seasons
Eg. Silver pine sheds pollen in October while red pine sheds in November

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Gametic isolation

Gametes from different species are often incompatible so even if they do meet they may not survive. This is due to chemical differences in gametes, sperm cannot penetrate the surface of the egg or the sperm may not survive in the reproductive tract.
Eg. Kina eggs cannot be fertilised by any other species sperm as they are released externally

18

Behavioural isolation

Differences in species behaviour, typically mating behaviour such as courtship
Eg. Female moths release pheromones to attract a mate which are species specific

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Mechanical/structural isolation

Differences in structure of external reproductive organs (incompatibility) prevents sperm transfer between individuals of different species
Eg. Damsel fly, plants with long corolla tubes pollinated by moths while short by bees

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Postzygotic isolating mechanisms

Hybrid sterility
Hybrid inviability
Hybrid breakdown

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Hybrid sterility

The hybrid reaches maturity but is sterile so cannot breed as genes cannot flow from one species gene pool to the other. Meiosis fails to produce normal gametes because chromosomes of the two parents are different in number or structure
Eg. Male donkey and female horse = sterile mule

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Hybrid inviability

A zygote, embryo or offspring may be produced but is inviable (unable to survive and develop normally) so dies early in its development. Fertilised eggs often fail to divide because of mis-matched chromosome numbers from each gamete.
Eg. Frogs

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Hybrid breakdown

When the hybrid reaches maturity it is able to breed (the first generation may be fertile) but the second generation are infertile or inviable
Eg. Cotton species

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Small scale biological evolution

Changes in gene frequency in a population from one generation to the next

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Speciation

The formation of new species, the result of reproductive isolation

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Reproductive isolating mechanism

Any factor that stops members of populations of the same species or different species from breeding together

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Ecological isolation

Differences in habitat within the same geographical area so that populations rarely come in contact
Eg. 2 species of herbivorous insect feed and mate on different plant species

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Geographical isolation

Physical barriers separating populations. This creates sufficiently different populations
Eg. Kaka and kea

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Hybrid

The offspring of two plants or animals of different species

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Ploidy

Number of chromosomes in a cell

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Polyploidy

Chromosomes are represented 3 or more times in an individuals genome

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Genome

The complete set of genes or genetic material present in a cell or organism

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Auto polyploidy

Involves the multiplication of the entire genome within a single species

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Allopolyploidy

Results in hybridisation between two different species. Advantageous to the polyploid produced should selection pressures change because it has genetic vigour

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Instant speciation

Results in a new species in a single generation because of polyploidy

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Punctuated equilibrium

Rate of evolution not steady. Long periods of statis followed by bursts of rapid speciation

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Adaptive radiation

Rapid evolution of a large number of species from an ancestral group to occupy a variety of different ecological niches that have become available suddenly

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Divergence

The emergence of two or more new species from a common ancestor

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Adaptive radiation occurs because:

The evolution of some new structural or physiological features that enable a group to occupy new niches or displace another
As a result of colonisation of new seas devoid of competitors

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Convergent evolution

Occurs when 2 or more unrelated species evolve to resemble each other as a result of being subject to similar selection pressures

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Co evolution

A biological process where one species acts as the selection agent for the evolution of another species

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Co evolution is often seen in relationships:

Mutalistic
Predator/prey
Host/parasite

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Geographical barriers include

Mountain building eg. Southern alps eventuated 2.5 mya
Climatic conditions eg. Ice age raised sea levels, NZ became 2 Islands

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Endemic

Found only in that country

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Ring species

Special case of a cline in which two ends of the cline join to form a ring or loop

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Immigration

Move into a population

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Emigration

Move out of a population

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Inbreeding

Breeding between closely related individuals
Takes place within a population and decreases genetic diversity

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Outbreeding

Breeding between non related individuals
Results in hybrid vigour

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Interbreeding

Takes place within different populations and increases genetic diversity

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Selecting agent

Individual environmental factors

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Founder effect

Small number of individuals dispersed to a distant island

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Bottleneck effect

Large populations reduced in size due to environmental event or human impact

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Resources include:

Food, shelter, nest sites, territories and mates

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Taxa

Classification groups (eg. Genus, family, phylum etc)

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Species concepts (what are the limitations to what a species is defined as?)

Asexual reproduction
Hybrids
Demes
Breeds
Clines
Cloning

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New Zealand geographical barriers

Mountain building (Southern alps)
Climatic conditions such as glaciation, rising sea levels and vegetation zones
Tectonic plate activity

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Aneuploidy

Only certain chromosomes are represented an unusual number of times

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Rates of evolution

Punctuated equilibrium
Gradualism

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Patterns of evolution

Adaptive radiation
Divergence
Convergent evolution
Co-evolution
Parallel evolution

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Evidence of evolution

Biogeography
Vicariance
Comparative anatomy
Genetic analysis
Biochemistry
Homologous structures
Fossil records
Analogous structures
Embryology

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Gradual mode (divergence)

Common ancestor diverges into new lineages so that ancestral species no longer exist

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Punctuated mode (divergence)

New lineages diverge from ancestral line so both new lineages and ancestral species exist

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Comparative anatomy

Study of similarities and differences between anatomies of animals

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Analogous structures

Structures that have the same function in different organisms that may come from different origins

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Homologous structures

Features that are similar in structure and origin but different in function

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Biogeography

Study of geographic distribution of species

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Vicariance

Large scale Allopatric speciation of a taxonomic group by a geophysical event

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Genetic analysis

Uses rates of mutation in mtDNA as a molecular clock

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mtDNA

Is inherited from the mother only and passes through maternal (female) line of the family

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Embryology

The study of early development of veterbrates

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Biochemistry

Determining the Amino acid sequence of DNA and protein.
Similarities of organisms of different species

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Fossil records

Occur in sedimentary rock (strata) and preserved remains of past organisms