14 ecosystems Flashcards
(23 cards)
An ecosystem is made up of:
· Abiotic factors are non-living factors. (physical and chemical)
· Biotic factors are due to the interactions of organisms in an area. (feeding relationships between organisms).
examples of abiotic factors
soil type
ph
co2 concentration
temp
light intensity
water avaliability
examples of biotic factors
food availability
predation
parasitism
disease
competition
There are two types of competition:
interspecific
intraspecific
- Interspecific competition.
Competition between different species – e.g. weeds and crop plants in a field competing for light, minerals.
· No two species can occupy exactly the same niche as there would be too much interspecific competition between them for the same resources.
· The more similar the niches of two competitors, the greater the competition will be between them.
- Intraspecific competition
This occurs between individuals of the same species for the same resource.
Predation
What effect will this decline in prey numbers have on the predators?
Less food results in more intraspecific competition, less reproduction, increased mortality so predator population decreases.
In response to this, what will then happen to the size of the prey population?
Fewer eaten, more survive to breed so population increases
Carrying Capacity
Populations within an ecosystem can only reach a certain size. The maximum size that a population can remain sustainable in a particular habitat is called the carrying capacity.
If the carrying capacity is exceeded, the population declines because its environment can no longer support the excess numbers.
Autotrophs
are the primary producers i.e. green plants and algae.
Heterotrophs can be:
· Primary consumers, i.e. herbivores, which feed exclusively on plants.
· Secondary consumers, i.e. carnivores, which eat herbivores.
· Tertiary consumers i.e. carnivores which eat other carnivores.
NB: omnivores are heterotrophs that can feed off both plants and other consumers.
important facts of energy flow (2)
· Energy flows only once through an ecosystem and is eventually lost as heat. Nutrients are continually recycled.
· Energy and nutrients pass through ecosystems from autotrophs to heterotrophs.
Food Chains and Webs
Energy flows through the ecosystem from one trophic level to the next. The first
trophic level is occupied by
primary producers,
the second by primary consumers, the third by secondary consumers and so on.
A series of trophic levels is called a food chain.
Saprobionts
These are organisms that digest the dead remains and waste products (detritus) of every type of organism, releasing inorganic molecules and ions.
These organisms are generally referred to as decomposers or saprobionts (also known as saprobiotic organisms) e.g. bacteria and fungi .
They secrete enzymes onto the detritus (extracellular digestion) and absorb the products of digestion.
Energy Transfer to Producers
The ultimate source of energy is the Sun.
Not all of the light energy that falls on a plant is used by the plants for photosynthesis. This is because:
· Some of the light does not fall on photosynthetic parts of the plant (e.g. the leaves) and even if it does it may not strike chlorophyll.
· Some of the light is not of an appropriate wavelength to be used in photosynthesis.
· Some of the light is reflected or transmitted through the leaf.
Biomass
This is the mass of organic material in an organism / ecosystem
Biomass can be measured in terms of mass of carbon, or dry mass of tissue, per given area.
Calorimetry
- The chemical energy store in dry biomass can be estimated using a bomb calorimeter.
- Dry material is burnt in oxygen. The energy given off heats up the water in the calorimeter.
- The rise in temperature can be used to calculate the energy (in calories) that was contained in the material.
Net primary production
is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
Gross primary production
GPP is the chemical energy store in plant biomass, in a given area or volume.
Net primary production = Gross primary production – Respiration
Calculating the Efficiency of Energy Transfer
Energy transfer = energy available after the transfer /
energy available before the transfer
x100
The transfer of energy to and between consumers also involves a loss.
Losses are due to:
· Some of the food taken in is not digested, therefore it lost in faeces.
· Some is lost due to excretion of metabolic waste products (e.g. urea)
· Some energy remains in parts of the organism that are not consumed (uneaten parts), e.g. roots of plants or bones/teeth of animals.
In all the above cases the energy is passed on to saprobionts.
· Most of the energy is lost due to consumer respiration.
· Eventually all energy lost is transferred to the environment as heat.
Explain how you would reduce the respiratory losses in cattle farming.
- Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production.
- Feed on concentrate /controlled diet /controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces / valid reason for addition.
- Movement restricted so less respiratory loss / less energy used.
- Kept inside/heating/shelter / confined so less heat loss / no predators.
- Genetically selected for high productivity.
Main events of succession
Hostile environment – colonised by pioneer species
Abiotic environment of habitat changed by pioneer species
The changed environment becomes more suitable to support new species
Establishment of new plant species increases the species diversity as various groups of animals enter the habitat; the early colonisers are replaced by new species
Changes in the abiotic factors result in a less hostile environment and an increase in biodiversity
A climax community develops
