unit d Flashcards
population
the number of individuals of the same species populating a given area at a certain time.
continuous variation
All individuals have the trait, just different extents
eg height
discontinuous variation
either have the trait or not
mutation
a random change in dna base sequence
underlying source for all variation
gamete mutation can be passed on to the next generation
gene pool
all of the genes that collectively occur within a population at a certain time
polymorphism
two or more varieties of same gene that are present and maintained within a population
natural selection
variation within a population due to mutations
survival of the fittest
speciation
random generic drift
not due to natural selection, but chance. typically impact small populations
independent assortment
if parents have small number of children all of the alles are not passed onto the next generation as only a few gametes are used
bottleneck effect
accidental chance events which kills a larger segment of the population such as flood, fire etc. surviving maybe very different from the larger population from which it arose
founder effect
small group breaks from the larger group and forms a new population
gene flow
transfer of alleles into or outside the population such as pollen
reduces differences between populations over time.
can increase or decrease the fitness of population
hardy-weinberg principle
no change in the phenotypic or the genotypic ratios if
infinite population size, no migration, no mutation, mating is random, each genotype has equal opportunity for reproductive success, female and male allele frequencies are the same.
p+q = 1
p = dominant
q = recessive
p(2) + 2pq + q(2) = 1
factors that determine the size of a population
emigration, migration, mortality, natality
carrying capacity (K)
size limitation, max number of individuals that can be sustained by a particular environment
J-curve
rapid growth
closed system (no migration)
food is abundant, reproduction at its biotic potential
eventually goes over k (carrying capacity) but comes down
S-curve
initially a j-curve but crowding and lack of resources will slow the population down
hovers around the carrying capacity
open system
environmental resistance limits continued growth and prevents from reproducing at their biotic potential
establishing carrying capacity
biotic potential
the highest possible per capita growth rate in ideal conditions
density dependent (biotic)
factors that influence the population growth or size in relation to population density
density independent (abiotic)
factors are not influenced by a species population size. All species populations in the same ecosystem will be similarly affected, regardless of population size. Factors include: weather, climate and natural disasters.
different phases
lag phase - starting point, low population numbers
exponential growth phase - more natality than morality, enough resources, exponential growth is the steepest
stationary phase - carrying capacity reached natality=mortality
death phase - more mortality than natality, depleted resources, possible change in carrying capacity
r-selected population life strategies
opportunistic
environment fluctuate, limited competition, no affect by crowding, usually small creatures, less parental care for offsprings, early reproductive age, high biotic potential, sudden environment change can cause massive deaths, rapid growth rate, short life span, adapting to changing habitats, populations may go pass their carrying capacity, J-curve
K-selected
equilibrium
stable environment, a lot of competition, crowding impacts, survival of the fittest, larger organisms, less and slow growing offspring, require more parental care, population around the carrying capacity, S-graph, low biotic potential
ecological succession
sequence of community and ecosystem changes after a disturbance
