Biology: Animal Orientation, Movement, Evolutionary Processes, and Speciation

Vocabulary flashcards covering key concepts from Animal Orientation & Movement, Basic Evolutionary Processes, and Speciation I & II.

Orientation

The ability of an organism to position itself in response to an environmental stimulus.

Taxis

A directional movement of an active organism towards or away from a directional stimulus.

Phototaxis

Directional movement in response to light.

Chemotaxis

Directional movement in response to a chemical stimulus or chemical concentration gradient.

Rheotaxis

Movement against/towards the source of a water current, e.g. salmon swimming upstream.

Kinesis

A non-directional movement response where an organism changes its speed or rate of movement according to the intensity of a stimulus.

Homing

The ability of an animal to return to a particular place, often across unfamiliar territory.

Migration

Regular, usually seasonal or annual, mass movement of animals from one region to another. True migration normally includes a return journey.

Navigation

The ability of an organism to determine its position and maintain a direction towards a destination.

Landmark navigation

Navigation using familiar visual features such as coastlines, mountains, trees or buildings.

Sun compass

Navigation using the position of the Sun to determine direction. A biological clock is required because the Sun changes position during the day.

Stellar navigation

Navigation using the patterns of stars.

Magnetic compass

Navigation using Earth's magnetic field to determine direction or position.

Polarised light

Light waves align in particular directions, allowing some animals to determine the Sun's position even when it is cloudy.

Allele frequency

The proportion of a particular allele in a population's gene pool.

Gene pool

All the alleles contained within a population.

Genetic variation

Differences in alleles, genotypes or phenotypes among individuals in a population.

Gene flow

The movement of alleles between populations when individuals or gametes migrate and successfully reproduce.

Genetic drift

A random change in allele frequencies caused by chance events. Its effects are strongest in small populations.

Founder effect

A form of genetic drift in which a new population has only a small and possibly unrepresentative sample of the original population's alleles.

Population bottleneck

A large, sudden reduction in population size. The few survivors may carry only a limited and unrepresentative sample of the original gene pool.

Natural selection

The process in which individuals with phenotypes better suited to the environment survive and reproduce more successfully, passing favourable alleles to their offspring.

Selection pressure

An environmental factor that affects an organism's ability to survive and reproduce, such as temperature, disease or competition.

Biological fitness

An organism's ability to survive and reproduce successfully in its environment.

Niche

The habitat occupied by an organism and its role within that environment.

Species

A group of organisms that can successfully interbreed and produce fertile offspring.

Speciation

The formation of new species.

Reproductive isolation

The prevention of successful interbreeding between populations, preventing gene flow and allowing them to develop into separate species.

Reproductive isolating mechanism (RIM)

A biological mechanism or barrier that prevents individuals from interbreeding and producing viable, fertile offspring.

Allopatric speciation

Speciation caused by geographical separation of populations.

Sympatric speciation

Speciation occurring without geographical separation.

Divergence

The accumulation of genetic and phenotypic differences between populations.

Prezygotic isolation

A reproductive barrier that prevents mating or the successful fusion of gametes.

Geographical isolation

Physical separation of populations by barriers such as mountains, rivers or glaciers.

Habitat or ecological isolation

Reproductive isolation caused by populations living in different habitats.

Temporal isolation

Reproductive isolation because populations reproduce at different times of the day, season or year.

Behavioural isolation

Reproductive isolation caused by differences in mating behaviours or courtship rituals.

Structural isolation

Biochemical differences prevent sperm and egg, or pollen and ovule, from recognising or fusing with one another.

Chemical or gametic isolation

The two organisms have different reproductive structures and therefore cannot mate successfully.

Postzygotic isolation

Interbreeding occurs between different species or genetically different populations, but the offspring have reduced viability or fertility.

Reduced hybrid viability or hybrid inviability

The hybrid embryo or offspring does not develop normally, has low survival, or dies before reaching reproductive age.

Hybrid sterility

Differences in reproductive structures prevent successful mating or the transfer of gametes. A sterile hybrid is produced.

Hybrid breakdown

The offspring of a hybrid are less viable or fertile than the hybrid itself.

Hybridisation

The process of mating or crossing individuals from different species or genetically different populations.

Non-disjunction

Failure of chromosomes to separate properly during meiosis, producing cells with abnormal chromosome numbers.

Autopolyploidy

Polyploidy in which chromosome sets come from the same species following chromosome doubling.

Allopolyploidy

Polyploidy in which chromosome sets come from different species following hybridisation and chromosome doubling.

Diploid — $2n$

A cell containing two complete sets of chromosomes.

Haploid — $n$

A cell containing one complete set of chromosomes.

Tetraploid — $4n$

A cell containing four complete sets of chromosomes.