Population size and Ecosystem (WIP)

ALEVEL edexcel

Ecology

the study iof the interactions of organisms within their environments, including biotic and abiotic factors

Ecosystem

ecological unit consitsting of several habitats and their associated communities with bioti and abiotic components. STABEL SELF-PERPETUATING SYSTEM

Population

group of interbreeding individuals of the same species occupying a particular place at a given time

Community

all organisms living in a particular habitat

Habitat

place where organisms live within an ecosystem. Where they live, feed and breed

Niche

refers to the way in which an organism fits into an ecological community of ecosystem

Population size

the number in a population

Population density

numbers in a population per unit area

What do population numbers depend on?

-Birth rate or rate of division/multiplication

-death rate

-emigration (movement out of population)

-immigration (movement into population)

Biotic factors increasing population growth rate

-high brith rate

-adequate food

-ability to compete for resources

-ability to defend agasint predators

-ability fo resist disease/parasites

-ability to adapt to change

Abiotic factors increasing population growth rate

-favourable light

-gavourable temperatures

-optimum level of nutrients/minerals

Population growth graph- exponential

under ideal conditions graph should be J shaped

Population crash

eventually an exponential graph will result in a “crash” caused by a density independent even

Population growth graph- s shaped

growth does not continue unrestricted

Population growth- lag phase

slow growth while it adapts to a habitat

population growth -log/exponential phase

rapid grwoth as there is lots of reproduction with little environmental resistance

population growth- stationary phase

birth rate of new individuals is equal to death rate of older ones. The population has reached the carrying capacity for the particular environment

bacterial populations- death phase

the build up of toxins in the closed environment l;eads to death rate being faster then multiplication rate

carrying capacity

the maximum population size that can be supported indefinitely by a given environment

Factors that may limit or slow population growth

-available food

-predators

-parasitism/disease

-overcrowding

-competition for… (be specific)

-accumilation of toxic waste

-weather

Density dependant factors

tendancy for the death rate to increase or birth/growth rate to decrease as density of population increases

a greater proportion die

density independant factors

the tendancy for the death birth or growth rate in a population to neither rise nor fall as the density increases

A fixed percentage of the population dies

Emigration

movement out of a population- non-reversable and trigered by overcrowding

Migration

periodic seasonal movement

Sampling techniques

-random quadrats, line and belt transects

ACFOR SCALE

what is competition

an interaction between two or more organisms or species.

-a regulatory factor

intraspecific compeetition

individuals of the same species striving for the same resource

interspecific competition

between individuals of different species

law of constant yeild

when density is sufficiently high and resources become limited the effects of competition will result in a constant biomass

interspecific seasonal competition

competitive exclusion principle

two species that compete for the same resources cannot stably coexists

-one competitor will have an advantage over the other which leads to extinction/ near extinction

ecosystem

the type of place where an organism lives

habitat

the specific parts of the ecosystem that meets thge organisms needs and in which it lives

community

all the animals and plants living in one habitat

trophic structure

represents the different feeding relationships that determine the route iof energy flow and the pattern of chemical cycling

hydrothermal energy and chemosynthesis

carbon dioxidde + water+ hydrogen sulfide + oxygen > carbohydrate + sulphuric acid

biomass

-the mass of living material within an ecosystem

-measured by weight or by dry weight per unit area of land or per volume of water

NPP

Net primary productivity- the potential food available to primary consumers

it is the organic mass of plants

the biomass added to an ecosystem per unit area per unti time

GPP

Gross primary productivity- the rate of production of chemical energy in organic molecules by photosynthesis (KJm^-2 year^-2)

ie- the rate at which products are formed

NPP equation

NPP= GPP-R

Factors limiting NPP

-low rainfall

-low temperature

-few available nutrients

-a short growing season

ecological efficiency

Succession

the change in structure and species composition of a community over time

seral stages progress towards a climax community

watch a video bro

primary succession

-colonisation of bare rock which becomes woodland

-no organic matter at first, colonisation by pioneer communities like algae and lichen

-increases the weathering of rocks> soil particles

-death of organisms provide organic matter

-small plants supported by thin slil replace pioneer organisms

-death and decomposition lead to thicker soil> flowering plants

-natural climax community

secondary succesion

-an area that previously supported life

-back to bare earth due to some reason

-has soil/organic matter

-plants are reestablished from seeds in soil

-quicker

facilitation

species interactions that benefit at least one of the species but with no harm to any of the species

Zonation

the change in species along an environment gradient- a spatial change in species

The carbon Cycle

1- photosynthesis removes CO2 from the atmosphere

2-production of carbohydrates, proteins, fats leads to plant growth

3-consumed by animals and therefore lead to animal growth through food webs

4- CO2 added to atmosphere through respiratiions
5- dead organisms acted on by saprotrophic microorganisms> more respiration added CO2 in atmosphere

6-partial decay of dead organisms in the past has lead to formation of fossil fuels- combustion of fossil fuels returns more CO2 to atmosphere

Human activity effecting carbon cycle

-combustion of fossil fuels acounts for about 70% of increase

-deforrestation accounts for about 30%

The greenhouse effect

-greenhouse gases allow high energy solar radiation to pass through to the earths surface

-much escaped to space as heat but some is trapped and absorbed by the gases into the atmosphere, heating everything up

causes of enhanced greenhouse effect

-increased human population >need more food, more recources and create more waste

-increased conbustion of fossil fuels

-more car exhaust emissions

-more cows and rice fields for food

-deforrestation

-more fertilisers

-CFCs

effect of climate change on organisms

-changing weather and vegetation patterns, forcing species to migrate to survive

-but the rapid nature is likely to exceed the ability for species to migrate or adjust

-increased sea temperaturs are causing more coral reefs to bleach

what is carbon footprint

the total amountof carbon dioxide attributable to the actions of an individual or product or service over a period of one year

the nitrogen cycle -assimilation

nitrates and ammonium compounds are taken up by plants to form amino acids and proteins

plant proteins are digested and formed into animal proteins

the nitrogen cycle- putrefaction or ammonification

-bacteria, plants and animals die or produce waste

-the process of decay of dead remains is alos known as putrefaction. Bacteria and fungi break down organic nitrogen in dead remains, faeces or urine into ammonia which forms ammonium in the soil

The nitrogen cycle - nitrification (aerobic)

Nitrosomonas convert ammonium into nitrites (NO2-)

Nitrobacter convert nitrites to nitrates (NO3-)

The nitrogen cycle- nitrogen fixation

Requires nitrogenase enzymes and ATP. Atmospheric nitrogen is converted into ammonia by:

Azotobacter (live in soil) and rhizobium (symbiosis, live in root nodules of legumes)

theres also atmospheric fixation with lightning and industrial fixation with the haber process

The nitrogen cycle- denitrification

Thiobacillus and Pseudomonas reduce nitrates back into nitrogen (anaerobic)

good human activity

-draining land and ploighing fields

-fixing atmospheric nittogen

-applying artifical fertilisers/ manure or slurry

How can fertilisers reduce biodiversity

extra nutrients allow fast growing plants to dominate, blocking smaller species’ acess to vital sunlight.