Conservation, human impact Flashcards
Competitive exclusion principle
no two species can occupy the same niche in the same environment for an extended period of time
defined Population:
A group of individuals of the same species living in the same place at the same time and interbreeding
Why individuals live in populations
• more successful in breeding and rearing their young
• gain protection from predators in a group
• locate new food resources in a group
Located where resources are, where danger is not and can migrate due to season changes
Patterns of dispersion:
- Uniform: e.g. planted forests, penguins
- Clumped: fish, plants (where water is)
- Random: rainforest
What determines population growth:
Birth rate (natality): Death rate (mortality): Immigration: Emigration: Net migration rate:
Rate = (births + immigration) – (deaths + emigration)
Define: Birth rate (natality):
the reproductive capacity of the population
Define: Death rate (mortality):
the death rate of organisms in the population
Define: Immigration:
is the movement of individuals into a population
define: Emigration
is the movement of individuals out of a population
Define: Net migration rate
the difference between immigration and emigration
2 types of Population growth
J shaped curve
S shaped curve
what is J shaped curve
If conditions are favourable, the birth rate will exceed the death rate and lead to exponential growth
what is S shaped curve
logistic growth curve. As the population increases it encounters resistance from the environment as it begins to fill the environment up.
This environmental resistance increases as the population overshoot the carrying capacity.
The population tends to fluctuate around an equilibrium level.
Define: Carrying capacity (k)
the maximum stable population size a particular environment can support
what is Environmental resistance
all the factors that may limit the growth of the population, such as accumulation of waste products, scarcity of resources such as food and space, or adverse climate conditions
2 Factors affecting population growth:
Abiotic
and biotic
what Abiotic factors affect population growth
Lack of shelter exposes individuals to harsh climates
Plants need light at the correct intensity, duration and wavelength if they are able to achieve optimum growth
Shortage of oxygen can limit the number of aquatic species
Water quality is affected by pollution and intolerant species may die
what Biotic factors affect population growth??
Plants and animals may have to compete for scarce resources such as food, water, light and space
Predators can reduce the number of prey species
The higher the density of the population, the more rapidly disease could spread through
Parasites reduce the ability of the host species to survive and reproduce
2 type of affecting population growth
Density-dependent factors
Density-independent factors
Density-dependent factors
vary on the effect they have on a population depending on the size (always biotic)
• Space, competition, predation, parasites
Density-independent factors
affect all plants and animals in a population irrespective of population size
• Severe storms, flooding, severe cold spells, earthquakes, volcanoes, meteors
what are Keystone species
A species that is not necessarily abundant in an area but has a strong control on the structure of the community due to its role or ecological niche (e.g. cassowary: dispersal of seeds)
Ecological Role of Fire in forest ecosystem
Fire reduces the probability of catastrophic fires: controlled fires can get rid of leaf litter
Nutrient input into soils: soil nutrients are usually tied up in organic matter released in pulse after fire
Control of insect pests: high temperatures and smoke can kill adults, larvae and eggs
Control of tree pathogens: spore germination and spread is inhibited by smoke
Maintains species diversity: some species are fire-adapted
what are Plants adoption to fire:?
vegetative reproducers: regrow through means of buds located under the bark or in underground stems
obligate seeders: the plants do not survive the bushfire but the seeds do and germinate after in the mineral-rich soil
What are Animals adaptions to fire?
Mobile organisms, such as birds and fast moving mammals may escape flames and avoid the lethal radiant heat by flying or running away
Slower moving animals escape by retreating into burrows or sheltering under thick bark where they are insulated from the fire
Some animals exploit opportunities provided by fire for feeding
define: Succession
The change in structure and species composition of a community over time
Primary succession
Succession that happens when an area is first colonised
Examples of primary succession
- A retreating glacier depositing rock
- Wind or sea piling sand into dunes
- Volcanoes erupting and depositing lava
- Land subsiding and creating lakes or ponds
- Silt and mud being deposited at river estuaries
Define: Secondary succession
Secondary succession is the series of community changes which take place on a previously colonised, but disturbed or damaged habitat
Define: Pioneer species
The first stage of succession involves pioneer species colonising an inhospitable environment
Pioneer species have features that suit them to colonisation (they have no roots)
Features of pioneer species
Production of a lot of wind-dispersed seeds to easily reach isolated areas
Rapid germination of seeds
The ability to photosynthesise
The ability to fix nitrogen from the atmosphere
Tolerance to extreme conditions
Stages of plant succession
Colonisers (lichens): when they die, they release nutrients. This changes the abiotic environment by creating soil.
Mosses, then Ferns: rock is continually eroded, as these die organic matter increases, building up soil
Small flowering plants: shrubs then trees establish
Climax community
The organisms that make up the final stage of ecological succession. A balanced equilibrium. The rainforests of SE Queensland are an example of a climax community
Common features in any succession
The non-living environment becomes less hostile A greater number and variety of habitats Increased biodiversity More complex food webs Increased biomass
Animal Succession
Animal species present depend on the plant species found in the area. For example, mosses and grasses provide food and habitats for insects and worms. These can then support secondary consumers
