terminology and population dynamics
terminology
-taxonomy:
-the science of grouping organisms according to similarities in their features
-any taxonomic group is called a taxon
-the grouping of organisms may be subjective and can change as new information becomes available
-domain, kingdom, phylum, class, order, family, genus, species
-species:
-a group of closely related organisms that resemble each other and can reproduce to form fertile offspring
-separate species may not be able to breed due to:
-differences in behaviour
-anatomical differences
-differences in the number of chromosomes would make fertilisation impossible
-very closely related species may be capable of producing fertile offspring but do not do so naturally (in captivity)
-naming species:
-species are given Latin names so ecologists in all countries can use them
-the first part of the name is the genus, 2nd is the species
-generally the common names of all taxa have lower case letters but some authorities use upper case letters for species names
-evolution:
-process that alters a species gene pool, it can sometimes separate gene pools until they diverge into different species
-driven by survival of the fittest
-over time evolution may produce isolated populations sufficiently different that they no longer interbreed
-although these species are genetically similar they are no longer able to breed (speciation)
-habitat:
-an area or location where a species / community lives
-ecological niche:
-the role a species plays in its habitat
-the way it uses resources and relationships to other species
-in the same habitat 2 species cannot occupy the same niche one will out compete the other and cause population reduction
-population, community and ecosystem:
-population = all the individuals of a single species that live in a area
-community = all individuals of a species that live in a certain area
-ecosystem = the combination of biotic and abiotic features of an area
-biome:
-a large geographical region with specific climatic conditions and community of species
-all the areas a species can be found named by characteristic vegetation
-distribution controlled by climatic factors
-biosphere:
-all of the planet earth inhabited by living organisms - land
surface, soil, water and atmosphere
species diversity and population dynamics
-extreme environments:
-abiotic - temp, and light limits / year
-low species diversity
-fragile ecosystems
-less extreme environments:
-biotic - predation, disease and competition
-near to carrying capacity
-high species diversity
-stable ecosystems
-birth rate:
-determined by the natural ability of the species to reproduce
-lower chance of survival -> higher birth rate
-death rate:
-controlled by environmental factors - disease, drought, predation
-R-selected species:
-can respond rapidly to low survival rates
-reach sexual maturity quicker
-produce many young
-disperse widely
-eg, mice and locusts
-K-selected species:
-recover slowly from pop. declines
-reach sexual maturity later
-produce few young
-live long
-human exploitation may cause unrepairable damage
-eg, whales and elephants
-maximum sustainable yield:
-an understanding of population dynamics is important in monitoring the survival rate and breeding success of a species and to assess its MSY
-MSYs the greatest exploitation possible without causing irreparable damage
-variables to forecast a change in pop. size:
-current pop.
-number of births and deaths
-immigration and emigration numbers
-factors that affect mortality rate:
-density independent factors: where pop. density has no effect on the chances of survival of an individual
-density dependant factors: factors where the chances of an individual surviving depends on the pop. density of a species
-carrying capacity:
-the greatest pop. a area can support indefinitely without causing damage
-artificial population control:
-intervention to control the population through culling to enable the species / habitat survive where natural control measures are no longer in place
-if:
-breeding rate of endangered species is low so captive breeding and release utilised
-culling of alien species
-indigenous predator removal -> over population
-more variable populations