Unit 7 - genetics, population, evolution and ecosystems Flashcards
Pioneer species
First species to inhabit an area
Primary succession
Where the land is completely bare
E.g. Following lava flow
Secondary succession
Where some soil is already present, e.g. A ploughed field, or bush fire.
Succession
The process by which a plant or animal community successively gives way to another until a stable climax is reached
When a species colonises an area, how might they alter the environment?
- make it less for an existing species, causing competition with the existing one.
- make it more suitable for other species with different adaptations, as a relust this species may be out-competed by the better adapted new species.
What features might a pioneer species have which makes they suit colonisation ?
- reproduce asexually, so can build the population quickly.
- produce large amounts of wind-dispersed seeds or spores, which can easily reach isolated situations.
- germinate seeds rapidly, so they don’t require a period of dormancy
- able to photosynthesise, as light is readily available but other food is not, so not dependent on animal species.
- the ability to fix nitrogen from the atmosphere due to few nutrients in the soil
- tolerance to extreme conditions
Deciduous
Term applied to plants that shed all their leaves together at one season
Climax community
When many species flourish and there is much biodiversity.
Common features during succession
- Abiotic environment less hostile, this leads to
- a greater number and variety of habitats and niches, which produces
- increased biodiversity, this causes
- more complex food webs, leading to
- increased biomass
Conservation
Active intervention by humans to maintain ecosystems and biodiversity.
Main reasons for conservation
Personal
Ethical
Economic
Cultural and aesthetic
Phenotype
The observable or biochemical characteristics of an organism.
Genotype
Genetic constitution of an organism describing all alleles an organism has
Codominant
When both alleles are expressed in the phenotype
Genetic crosses
Method of representing parental gametes as well as finding out the offspring genotypes
Dihybrid inheritance
Two characters determines by different genes located on different chromosomes are inherited in this way
Sex linkage
Any gene carried on the x or Y chromosome
Autosomal linkage
Two or more genes carried on the same autosome
Epistasis
When one gene affects the expression of another
Chi squared
Compares the difference between sets of observations and expected results
Hardy weinberg
Equation used to estimate allelic frequency in a population subject to certain constraints
Disruptive selection
Selection favouring the extreme phenotypes
Allopatric speciation
Speciation where two populations become geographically separated
Sympatric speciation
Speciation of a population within the same geographical location because of new factors introduced
