Genetics and Variation - Ecosystems Flashcards
define discontinuous variation
organisms fit into distinct categories with no overlaps
controlled by a small number of genes
largely unaffected by environment
define environmental variation
variation where the environment determines where an organism lies within the limits
genes also set limits
usually due to polygenes
what is an example of environmental variation?
height or weight
define continuous variation
no categories to place individuals
controlled by polygenes
significantly affected by environment
forms a normal distribustion curve
define selection pressure
factors that cause competition for survival eg predators, disease
define genetic drift
the change in frequency of an allele in a population over time
where does genetic drift occur most often?
in smaller populations
what is the difference between the founding population and new population in genetic drift?
founding population has a small no. individuals with small no. alleles
new population has non-representative allele frequencies compared to parent population
define speciation
the evolution of a new species
what are the 3 steps of speciation?
gene pool isolation
evolution due to environment
reproductive isolation - organisms can no longer breed with members of original species to produce fertile offspring
what are the 2 causes of speciation?
allopatric speciation
sympatric speciation
when does allopatric speciation occur?
when organisms are geographically separated and each population experiences different selection pressures
when does sympatric speciation occur?
random mutations occur that cause an organism to be reproductively isolated from other organisms
normally requires organism to be able to reproduce asexually
what are the 4 causes of reproductive isolation?
seasonal changes
mechanical changes
behavioural changes
chromosomal changes
define ecology
the study of organisms in their environment
define abiotic factors
non-living parts of an environment
define biotic factors
living parts of an environment
define a community
a group of different species that live in the same place at the same time
what is an ecosystem?
biotic and abiotic factors and a community of organisms in a specific area
what is an environment?
the conditions that surround an organism, including both abiotic and biotic factors
what is a habitat?
the location where an organism lives
define niche
the role a species has in its environment, governed by adaptation to both biotic and abiotic conditions
what is a population?
all of the members of a species living together in the same place at the same time
