3.7.4 Ecosystems (C19) Flashcards
define community
all living organisms of all species found in a given area/habitat/ecosystem at a given time
define ecosysytem
self contained area including all the living (all the communities within it) and non living factors interacting with one another
define niche
describes how an organism fits into the environment/its role in the ecosystem - no organism can occupy the same niche
define succession
used to describe changes that occur over time, in the species that occupy a particular area
define abiotic
non living factor in the environment of an organism e.g temperature, oxygen concentration, pH, light
define biotic
the living factors in the environment of an organism e.g. disease, predation, competetion
define population
all of the organisms of one particular species in a given habitat/area at the same time
What conditions are necessary in order for the mark release recapture investigations to be valid? what assumptions are made?
- markings dont make organism visible to predators
- markings dont harm the organism
- No migration/immigration
- sample large
- no reproduction
- no births or deaths
- markings are nor easily rubbed off/worn off
- marked individuals in 1st sample distribute themselves evenly back into the population
Name two types of competition
interspecific and intraspecific
Define intraspecific competition
competition between organisms of the SAME species
Define interspecific competition
competition between organisms of DIFFERENT species
What is a pioneer species?
the first organism to colonise in the first stage of succession - it can with stand hostile environments
define a climax community
A stable community/no further succession.
All the organisms that make up the final stage of succession - animals and plants
define a habitat
place where an organism lives
define carrying capacity
The population size of a species that an be supported by the ecosystem
within an ecosystem which 2 major processes occur
- flow of energy through the system
2. recycling of nutrients within the system
define population size
the number of individuals in the population
what do we call factors that limit the size of the population
limiting factors - they can be abiotic or biotic
Give examples of abiotic factors that limit the size of a population
light, temperature, pH, water, humidity
give examples of biotic factors that limit population size
availability of food, predation, disease
The growth and size of the human population depends on
birth rate v death rate - its the balance between these two that determines if if increases, decreases or remains the same (also includes immigration and migration)
define immigration
when people move into a population from outside
define emmigration
when people move out of a population and leave
In a stable population what can be said about birth and death rates?
they are equal
In an increasing population what can be said about birth and death rates?
birth rates are higher than death rates
define predation
where one organism is consumed by another
Define prey
An organism that is consumed/hunted by another organism
Define a predator
An organism that hunts and feed on other organisms
Why is it impossible to count every organism when investigating populations?
too many to count, too time consuming, would probably damage the habitat
How do we ensure the samples we take are representative when investigating populations
Take large sample, sample at random
Name two types of quadrats
frame and a point
How does a point quadrat work?
A long pin is dropped along a horizontal bar at set intervals and the organism record that touches the pin
How does a quadrat work?
placed at various locations at random and the abundance of each species within the quadrat is then recorded
Describe how you sample at random
- lay out 2 tape measures at right angles along the area to study
- obtain a set of coordinates by a random number generator
- place the quadrat at the intersection of the coordinates and record the species present
define abundance
the number of individuals of each species in a given area
Abundance can be measured in two ways
- frequency
2. % cover
To ensure your results are reliable and representative you should
make sure your sample size is large
What does the mark release recapture technique allow you to do?
estimate the population size of organisms that move
state the formula for mark release recapture
est pop size = (total no of organisms in 1st sample x total number in 2nd sample)/ number of marked organisms recaptured.
Name the first species to colonise in the first stage of succession
pioneer species - they an withstand the hostile growing environment
What features might pioneer species have that make them able to colonise
- reproduce asexually
- produce a vast amount of wind dispersed seeds/spores that an reach isolated areas
- rapidly germinating seeds
- ability to photosynthesise
- ability to fix nitrogen
- tolerance to extreme conditions
Name pioneer species example capable of surviving inhospitable conditions
lichens
What species follows after lichens - why?
Mosses - this is because the environment becomes more hospitable, abiotic factors are changing
What species follows after mosses in succession?
ferns
How does succession impact on animals?
they have undergone successional changes too - largely determined by the different types of plants available for food and habitats!
The common features of succession include
- abiotic environment becomes less hostile
- greater number of and variety of habitats and niches
- increased biodiversity
- Increased variety of food sources
- more complex food webs
- increased biomass
Name the two types of succession
primary and secondary
what is the difference between primary and secondary succession
primary - bare land - no soil - takes longer to reach a climax community
secondary succession - felled areas - soil present - climax community reached sooner/more quickly
what is conservation?
The management of the earths natural resources by humans for the future
What does conservation of habitats involve?
active human involvement
What are the main reasons for conservation?
- maintain our planet
- Other species have occupied the planet longer than we have - respect
- living organisms contain a huge pool of genes that can make useful products/substances - could prove valuable in the future
- Habitats and organisms enrich our lives and many people find inspiration from them
what do you call the maximum stable population size of a species that an ecosystem can support?
carrying capacity
A predator is…
an organisms which kills and eats other organisms
predator and prey populations are said to be…
linked - when one increases the other increase (shortly after)..
what is a quadrat?
a square frame enclosing a given area
what equipment can you use to investigate non-motile organisms (e.g. plants and limpets)
quadrats and transects
What technique do you use to investigate motile organisms?
mark release recapture
What is species frequency?
How often a species is found
What would you set up if you wanted to investigate changes in plant distribution and environmental factors?
transect - place quadrat at regular intervals along the length and determine % cover (of chosen plant). Measure the environmental factor at that point too
Succession is…
how an ecosystem changes with time
During succession what changes?
Biotic conditions change as the abiotic conditions change
Primary succession …
happens on bare rock
secondary succession occurs…
on land that has been cleared/felled areas
What are the abiotic condition like at the start of succession?
harsh
What does the pioneer species do to the abiotic conditions?
changes them to make it less hostile so other species can begin to colonise
Does the pioneer species survive?
No it will die and be decomposed and add to the soil.
What happens to biodiversity as succession continues?
increases
The final stage if succession is called?
climax community
What sorts of activities prevent succession?
mowing lawn, animals grazing, managed fires
give 2 features of a climax community
- Same species present (over long time) / stable community (over long time);
- Abiotic factors (more or less) constant (over time);
- Populations stable (around carrying capacity);
How do you use the mark release recapture to determine the population of species A?
- Capture/collect/sample, mark and release;
- Leave time before second sampling/collection;
- (Population =) number in first sample × number in second sample divided by number of marked in second sample/number recaptured
Describe MRR
Take a sample of a population
Mark them in a way that is not toxic so will not harm them or hinder their chances of survival
Release them back into the population
Allow time for them to redistribute
Collect a second sample
Count how many are marked in the second sample
(N1 x N2) / N marked in 2nd sample
What are some issues if there isn’t conservation?
CO2 levels and impact on climate change
Reduces Biodiversity
Reduces habitats
Useful organisms may become extinct (e.g. for medicines)
Why should we conserve ecosystems?
Economic – able to keep using the area/tourism
Biological – reduces biodiversity, food sources and habitats
Ethical – we should prevent damage by humans and help those species effected by us
Aesthetic – looks pretty, is a nice place to be
Describe Succession
Pioneer species colonises an area with hostile conditions
This leads to changes in the abiotic factors
The conditions become less hostile
Other species are able to colonise the area
Conditions continue to change and become less hostile and new organisms outcompete the pioneer species increasing biodiversity
Eventually conditions become favourable to a climax community
The climax community has stable abiotic factors, stable populations, stable communities
