Ecology

Question	Answer
Ecology definition	The study of living things and their interactions with each other and their environment.
Population definition	An interbreeding group of organisms of the same species occupying a particular habitat
Ecosystems definition	A characteristic community of interdependent species interacting with the abiotic components of their habitat.
Birth rate definition	The reproductive capacity of a population; the number of new individuals derived from reproduction per unit time
Population definition	All the members of one species in an area that can breed with each other.
Community definition	All the members of all species in an area.
Habitat definition	The place in an ecosystem where an organism lives.
Immigration definition	The movement of individuals into a population of the same species
Equilibrium species definition	Species that control their population by competition rather than by reproduction and dispersal
Ecosystem changes	An ecosystem is not a static component; things change all the time. The source of energy for ecosystems is the sun. In temperate climates, the duration and intensity of sunlight changes over the course of a year, so the energy that flows through the ecosystem is subject to change.
Ecosystem changes pt 2	Nutrient cycles depend on fungi and bacteria, and their population growth is dependent on temperature (amongst other abiotic and biotic factors), so nutrient cycling varies throughout the year- ( cyclic pathway by which nutrients pass-through, in order to be recycled and reutilised. The pathway comprises cells, organisms, community and ecosystem.)
Factors controlling population size	Intensity of energy flowing through an ecosystem varies Biological cycles eg nitrogen cycle vary the mineral availability Habitats change over time as succession occurs New species arrive and some are no longer present Climate change alters habitats
Ecosystem changes pt 3 population	Community composition can change over time, for example, ponds silt up and land plants become established, this is known as succession. Population sizes change over time.
Things affecting population size	The population size is dependent on 4 factors – the reproduction rate, the death rate, immigration and emigration. In a stable population these are balanced and can be expressed as an equation: Reproduction + immigration = death + emigration This is because reproduction and immigration increase the size and death and emigration decrease the size of the population.
What determines population size	Birth rate, Immigration= increase pop Death rate or mortality,Emigration= decrease pop When combined effects of birth and immigration exceed death and emigration pop increases
Population size- fugitive/ equilibrium	Different strategies for population growth are used by different species, depending on characteristics- there's fugitive and equilibrium species
Fugitive	Fugitive species are poor at competition- instead rely on large capacity for reproduction/ dispersal to increase numbers- invade a new environment rapidly
Equilibrium species	Control population by competition in a stable habitat- usual pattern of growth is sigmoid- s shaped- curve called one step growth curve
Diagram of pop growth	p64
Niche definition	The role of an organism in an ecosystem, generally a feeding role.
Biotic	All the living and organic components of an ecosystem.
Abiotic	All the non-living parts of an ecosystem.
Population size- lag phase	Initially pop doesn't increase - period of slow growth- period of adaptation/ preparation for growth- rehydration and intense metabollic activity, especially enzyme synthesis- in sexually reproducing organisms- lag phase represents time for individuals o reach sexual maturity, find a mate and gestate young
Growth curve- what is it	Populations colonizing new environments undergo a characteristic series of stages that can be presented graphically as a growth curve. When writing about animals we tend to use the term birth rate rather than reproduction – careful not to use this for bacteria or fungi.
One step growth curve- bacteria	Bacteria in a nutrient broth first go through a lag phase. They are synthesising enzymes and replicating DNA. The numbers of individuals rise slowly. As food availability is high, the growth becomes exponential. Therefore, the cells divide rapidly, reproduction exceeds death rate and the population doubles for each unit of time. This is the log phase.As nutrients start to run out or get depleted, the reproduction and deaths in the population stabilise, this is the stationary phase. Death and reproduction are equal.Eventually the toxins in the broth build up to such an extent that deaths exceed reproduction and the population decreases in the death phase. Death could also be caused by nutrients running out in the broth.
But...	However, in less artificial situations other factors play a part- same factors apply but are additional biotic factors eg predation, parasitism/ disease as increased pop density allows infection to spread more rapidly, competition w/ other species for nesting sites and food- also abiotic factors eg temperature, light intensity (eg plants).
One step growth curve- animals- lag/ log phase	The lag phase is when the animal first arrives in an area, e.g. when grey squirrels were first introduced to Britain. The population increases slowly at first, there are not many individuals to breed and time is needed for enough individuals to reach sexual maturity. Log/ exponential phase- With plenty of food, the population increases exponentially.
One step growth curve- animals-stationary phase	Competition for food, territory and habitats is low; this is the log phase. Eventually the population reaches a maximum, called the carrying capacity- this number depends on resources available eg more food increased carrying capacity- pop= not absolutely constant fluctuates around cc in response to environmental changes
One step growth curve- animals-death phase	The factors that slow pop growth at end of log phase become more significant- pop size decreases until death rate is greater than birth rate- graph has negative gradient
Environmental resistance and carrying capacity	Predators= usually larger than prey and tend to kill before eating- abundance of prey limits no. predators and no. predators affects no. prey- predator-prey relationship causes both populations to oscillate (back and forth)-- oscillations limited by negative feedback (the effect that change in one part of an ecosystem or social system has on the very same part after passing through a chain of effects in other parts of the system)-
Negative feedback example	eg predators cause no. prey to decrease--- lack of prey- predators decrease--- lack of predators prey increases--- more prey predators increase- population numbers at carrying capacity can depend on numbers in other species
Calculating pop increase from a graph	When pop increase is very large- eg pop of bacteria in test tube- range of numbers is too great to plot on a linear scale- A log 10 scale is therefore used- each mark on pop size is ten times previous mark- shift log to see what population actually is- growth rate- no. species at certain time- no.species at another time (pop growth)/ time- no.species at both times antilogged to get proper amount
other calculations	for less than 1000 in pop: Birth rate: increase in pop/ original pop - to get to percentage- divide to 100- same structure for death rate over 1000- (Number of live births / Total population) * 1,000- will give you per 1000- eg if 4000- times no. by 4 net migration rate-: N = (I - E) / M X 1,000 N = Net migration rate I = Number of immigrants entering the area E = Number of emigrants leaving the area M = Mid-year population
Factors that regulate population increase- density dependent	Some environmental factors have more effect on given population if given area is larger- factors affect greater amount of population if pop is denser- called density dependent factors- biotic factors- include disease, parasitism and depletion of food supply
Factors that regulate population increase- density independent	Effect of abiotic factors in environment does not depend on population density- effect is same regardless of size of population- usually due to a sudden change in an abiotic factor eg flood/ fire
Populations fluctuate in numbers	Balance between birth rate and death rate regulates the size of a population- doesn't stay stay constant- in equilibrium species - usually fluctuations aren't large or erratic- numbers in populations fluctuate around a set point- if population rises above set point density dependent factor increases mortality or reduces breeding to extent that pop declines If pop falls below set pointr- environmental resistance is relieved for a bit- pop rises again
look at diagram for negative feedback	p69 lol
Abundance and distribution of organisms in a habitat	The study of species abundance and distribution= biogeography- Alfred R Wallace was first to model biogeographic regions- defined 6- when studying birds and other vertebrates- saw mountain ranges marked boundaries of many species' ranges and saw different animals in similar habitats- didn't correspond with prevailing exp that all organisms were created to suit particular environment
New habitat	When new habitat is assessed- physical features eg soil type and temp are described first- determine no./ type of plants that live there- also dependent on weather that usually occurs- animals in a habitat depend on plants- so in new habitat- plants described before animals
Measuring abundance	Abundance- no. individuals in a species in a given area or volume- can be assessed by: capture, mark, release, kick sampling in a stream and counting aquatic invertebrates
Measuring abundance plant species	Using quadrat to calculate the mean number of individuals in several quadrats of known area to find the density eg no./metre^2 Estimating % cover of a plant in which individuals are hard to recognise- estimating % frequency

Next up

Description

Resource summary

Similar

	Created by Darcey Griffiths 28 days ago