population and communities Flashcards
population
interacting groups of organisms of the same species living in an area
what happens populations of the same species live far for long
they will develop new characteristics and become different species
estimation of population size by random sampling
instead of counting individuals, we can count a sample from a small area and multiply this by total area of habitat
quadrat sampling
method used to take a measurement of an area without systematically deciding where to take it. it eliminates bias which may influence the measurement. this can work out population size or stationary animals and plants
explain in detail random quadrat sampling to estimate population size for sessile organisms
- a base line along the edge of the habitat using measuring tape
- generation of random numbers using a table or generator
- first random number= distance along tape, 2nd random number is distance across the habitat at right angle from tape
- quadrat is places precisely at the distance
capture- mark- release- recapture
used to calculate population size
when measuring mobile organisms must use traps, nets, etc
population size
=n1xn2/n3
n1= 1st capture total
n2= total, marked + unmarked
n3= 2nd capture, marked only
carrying capacity
maximum size of a population that an enviorment can support
2 types of limiting factors
density dependant factors
density independant facotrs
density dependant factors
factors that depend on population size:
food and water
space for territories
availability of mates
diseases
density independant factors
factors that affect populations in similar ways, independant of population size:
enviormental change
injury
build up of toxic products
old age
how do dependant factors affect a population
dependant factors will cause the population size to fluctuate due to a negative feedback control. the population oscilates around its carrying capacity.
population size curve
exponential stage, transition stage, plateu stage
exponential stage
births+ immigration> mortality + emigration
there are lots of supplys, resources, growth limited by population size
transition stage
birth + mortality > mortality + emigration
population growth is slower than start since now there are limiting factors and competition
plateu stage
limiting factors have restricted growth
mortality= births
population size formula
mortality + imigration)- (mortality + emigration)
modelling a sigmoid curve
place plant in container
count number of leaves everyday until surface is covered
plot results
community
all of the interacting organisms in an ecosystem they have beneficial or harmful relationship
intraspecific interaction-
effects that individuals of the same species have on other members of that species eg: competing
interspecific
effect that individuals hof different species have on one another: prey x predetor
types of competition
- competing for resources
- competing for mates
- pollen distribution to pollenators
- space + nesting sighns
types of cooperative
comunal roosting
shared parenting
group hunting
social predation
interspecific relationships
herbivory, predation, competition, parasitism, mutualism, pathogency
commensalism
interspecific relationship between individuals in which one species obtains food or other benefit from other without harming or benefiting the latter
examples of comensalism
- orchids growing on branches
- whales and barnacles
- tree frog on plant trees
- scavangers for food
mutualism
interspecific mutualism occurs between members of different species. both species benefit from relationship
examples of mutualism
- leguminous plant nodules and nitrogen fixing bacteria, bacteria provide nitrate, legumes provide oxygen
- fish eating food off whales teeeth
- reef building coral and algae- algae provide organic matter to coral, coral provide support
parasitism
interspecific relationship between species where one organism obtains benefits from another while inhbiting the benefits from another. the parasite lives in or on the host
parasitism examples
- ticks in deers sucking their blood
- leaches and tapeworm
- tongue biting parasite
predetor prey relatshionship
interspecific relationship where one organism eats another
predetor prey examples
rabits eating grass
bear eating fish
snake eating eggs
symbiosis
interaction between two different organisms living in close physical association, typically to the advantage of both
explain mutualism as an intraspecific relationship, root nodules in fabacea
fabacea are a large plant family including peas and beens. many of them have developed mutualistic relationhips with rhibozium bacteria absorbs N2and coverts it to NH4 to produce proteins. prevents plant from nitrogen degiciency.
mychorrhizae in orchidae
the roots of most plants from an association with fungi, called mychorizae in soil. the fungus absorbs nitrogen, phospherus, fized carbon and water from the soil and supplies them to the plant. orchid seeds to not contain food reserves so they need these nutrients. orchid supplies the fungus with carbon compounds from photosynthesis
zooxanthallae in hard corals
hard corals secrete Caco3 to form a skeleton where individual animals ( called polyos) can live. this provides a safe and protected envirment for the zooxanthallae to stay close to sunlight. the algae supply the coral with glucose amino acids and co2. coral provides co2 from cellular respiration from photosynthesis to the algae
top-down interaction
controlacts from the higher trophic level to lower one. an increase in predetor number will decrease the population size of the prey
bottom-up interaction
control acts from lower to higher trophic level. population of producers may be limited by number of nutrients in soil or water.
allelopathy and secretion of antibiotics
organisms that developed special waus as a part of their metabolic pathways to deter potential competitors from their ecological niche. these pathways are producing secondary metabolides which are not essential for its growth or its function.
example of allelopathy
fungi produce antibiotic substances which prevent the growth of other species by interfering with its cell wall
allelopathy defenition:
the realease of chemicals as toxins by plant, which are given off into the soil to prevent nearby competetive plants to grow in the same area
competetive exclusion
dows not allow two species to occupy the same ecological niche indefinatley. invasive species compete for resources with endemic species and often cause theme to occupy smaller niches, declining in population size or becoming extinct
endemic species
species which occur naturally in a ecological niche in a area. density dependant factors usually control and regulate population size.
invasive/alien species
humans deliberatley or accidentley introduced species which dont have native predetors
test for interspecific competition
positive association- species found in same habitat
negative association- species occur seperatley in different habitats
no association
expected values formula
row total x column total / grand total
