A3.1, C4.1 - diversity of organisms, populations and communities

small topics note wise

biological species concept

group of organisms that closely ressemble which can interbreed and produce fertile offspring

if the offsprings aren’t fertile, they are hybrids

two factors which cause variation

• genetic factors

• environmental factors

morphological concept of species

putting organisms into groups/ species based on appearance ( eg nmbr of stamens )

binomial system of classification

two names

in latin as it was the primary language

allows to maintain native term for language

sexual dimorphism

differences in characteristis between the different sexes of a species

evolutionary species concept

relies on genetic data and emphasises distinct evolutionary links between groups

ecological species concept

relies on detailled information about how organisms interact with their biotic and their abiotic environment

level of species

kingdoms => phylum =>

class => order =>

family => genus (genera) =>

species

king prawn curry or fat greasy sausages

population

group of individuals of the same species living in the same habitat at the same time

what is speciation ?

the process by which new species form, where one species is split into two or more species

allopatric speciation

geographic barrier separating population, preventing them from interbreeding

sympatric speciation

• prezygotic barrier: not allowing fertilisation to happen=> different behaviors which prevent them from breeding together ( temporal, behavioral, habitat

• postzygotic barrier: no fertility for offspring, or unability to develop into foetus

carrying capacity 

the maximum number of individuals of a species that can be supported by a given environment , due to limiting factors 

density of population

population per area

population

number of certain organism from a certain species in a point in time

density-dependent factors

control population size and keep a stable population close to carrying capacity. acts by raising death rate or lowering birth rate

internal density-dependent factors

caused by something in the population; fertility or breeding territory

external density-dependent factors

caused by something other than the population; ie pathogen or pest introduction 

densitity independent factors on population effect

does NOT bring towards carrying capacity, but does cause fluctuations

sigmoid shaped population curve

• lag phase: slow population growth

• exponential phase: conditions are ideal and maximum growth rate occurs

• transitional phase: growth rate slows, eventually reaches carrying capacity

• plateau phase: population reached carrying capacity, no growth (except for oscillations ) 

• decline phase: environment changes, cannot support population anymore, population crashes.

competitive exclusion

when alien species becomes invasive, and excludes species which are endemic to the area

competitive exclusion studies

read from book

allelopathy

chemical interactions between organisms where one species releases substances into the environment that affects the growth, survival, or reproduction of other species. These substances can inhibit competitors or pathogens, gibing the producer an advantage.

allelopathy in plants - 2 examples

garlic mustard releases compounds that inhibit funghi ( which increase carbon fixing ), reducing nutrient intake for neighbouring plants.

the black walnut tree produces juglone into the soil, which inhibits root development and photosynthesis in nearby plants.

allelopathy of microbes

penicillin ( the funghi ), produces penicillin, which kills bacteria by blocking bacterial enzymes needed for cell wall formation

streptomycin (bacteria ): secretes streptomycin into the soil, to supress other bacteria to not have to compete with other bacteria