7.4 Populations in ecosystems Flashcards
What are the 2 types of environments
- Harsh
- Mild
What makes it a harsh environment to live in
- Limited water
- Salty/ saline
Why is there less life in harsh environments
It’s harder to adapt to the abiotic factors which determine the survival
What type of factors determine the survival in harsh environments
Abiotic
Is there a lot of competition in harsh environments
No
Is there a lot of competition in mild environments
Yes
Why is there a lot of life in mild environments
Because many species are able to adapt to the biotic factors which determine survival
What type of factors determine the survival in mild environments
Biotic
What are the 2 shaped graphs that show population growth
- J shaped curve
- S shaped curve
What is another name for the J shaped curve graph that shows population growth
Boom and bust
Generally what type of population does the J shaped curve show
Pest insects population around agriculture
What is the biotic potential on a s shaped graph that shows population growth
The maximum rate of reproduction in ideal conditions
Why cant populations naturally reach their biotic potential
Because of environmental resistance - not always ideal conditions
What does carrying capacity mean
Maximum population size the environment can support
What does environmental resistance mean
A factor that limits population growth - both biotic and abiotic factors
Define population
Individuals of the same species in the same area at the same time
Define Community
Populations of different species living in the same habitat at the same time
Define niche
The organisms role within ecosystem
What is a fundamental niche
The role the organism could play in the environment
What is a realised niche
The actually role the organism plays in the environment
What is competition between
Individuals
What is interspecific competition
Competition between individuals of different species
What is intraspecific competition
Competition between individuals of the same species
What type of competition has a greater effect, inter or intra
Intraspecific competition because the fundamental niches are exactly the same so one of the individuals will be restricted only to their realised niches
Define abundance
The number of individuals existing in a habitat
What is the mark-release-capture equation
P= (N1 x N2) / R
What do the letters P, N1, N2, and R mean in the mark-release-capture equation
P= estimated population size
N1= Total number of individuals in the first sample
N2= Total number of individuals in the second sample
R= Number of marked individuals recaptured
What are the 4 assumptions made by the mark-release-recapture method
- There are few births/ deaths in the population
- Proportion of marked: unmarked in 2nd sample is the same proportion in the whole population
- Marked individuals distribute themselves evenly among rest of population
- That the method of marking hasn’t been rubbed off/ toxic/ going to make them more conspicuous to predators
What is the minimum number of quadrats required to measure distribution
20
What are the 2 ways to position the quadrats
- Random
- Systematic
How do you select the coordinates for a random sample
By using a random number generator
What type of environment would you use a random sampling technique
A uniform
What are the 2 types of transects
- Belt
- Line
What is the difference between a belt transect and a line transect
A belt transect measures the abundance in each quadrat whereas a line transect measures everything that touches the line
What type of environment would you use systematic sampling
Non-uniform
What are the letters for standard deviation in biology
sx
Define species richness
A measure of the number of different species in a community
Define ecological succession
The change in environment over time
What is a sere
A complete succession of plant communities which result in the climax community
What is a primary succession
A site of newly formed habitat not previously supported community
What is a secondary succession
A site that has previously supported a community
Define ecosystem
A community and the non-living/ abiotic components of the environment
Define species diversity
The number of different species and the number of individuals of each species within any one community
Define genetic diversity
The variety of genes possessed by the individuals that make up a population of a species
Define ecosystem diversity
The range of different habitats from a small local habitat to the whole of the Earth
What is meant by the term species richness
The number of different species in a particular area at a given time
What type of system are ecosystems
Dynamic
What are the 2 major processes within an ecosystem to consider
- The flow of energy through the system
- The cycling of elements within the system
What is a population
A group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed
What 2 major things can cause variation in the size of a population
- Effect of abiotic factors
- Interaction between organisms
What is a community
All the populations of different species living and interacting in a particular place at the same time
What is a habitat
The place where an organism normally lives and its characterised by physical conditions and the other types of organisms present.
What is a niche
It describes how an organism fits into the environment. it refers to where an organism lives and what it does there
Does a niche include all the biotic or all the abiotic factors to which an organism is adapted to survive, reproduce and maintain a viable population
Both, both the abiotic and biotic factors are included
What is known as the competitive exclusion principle
No 2 species occupy exactly the same niche
Why don’t populations continue to grow indefinitely, give a few examples
Because certain factors limit growth
e.g. food availability, light, water, oxygen, shelter, accumulation of toxic waste, disease, predators
The population size of a species that an ecosystem can support is known as
The carrying capacity
How does temperature influence the size of a population
- Each species has a different optimum temperature at which it is best able to survive- the further away the temperature is to the optimum = fewer individuals in a population able to survive.
In plants and cold blooded animals, falling temperatures causes enzymes to work more slowly and a reduce in their metabolic rate. An increase in temperature causes denaturing enzymes. Both of these cases reduce the carrying capacity
In warm blooded animals, they can maintain a relatively constant body temp, however when the temp moves further away from their optimum the more energy the organisms uses to maintain their body temp. Leaving less energy for growth so slower maturity so slower reproductive rates = reduced carrying capacity
How does a drop in temperature effect the carrying capacity in cold blooded animals and plants
If the temp falls below the optimum the enzymes work more slowly and so their metabolic rate is reduced resulting in the population having a smaller carrying capacity
How does an increase in temperature effect the carrying capacity in cold blooded animals and plants
An increase above the optimum temp results in the enzymes working less efficiently since they gradually undergo denaturation which reduces the population’s carrying capacity
How does temperature change effect the carrying capacity in population with warm blooded animals
Warm blooded animals can maintain a relatively constant body temp, however if the temp moves further away from the optimum living temp for the animal, the animal then uses a lot of energy trying to keep their body temp, which leaves less energy for individual growth and so they mature more slowly and their reproductive rate slows = reducing populations carrying capacity
How does light effect the carrying capacity of a population
Increased light intensity increases rate of photosynthesis - faster growth of plants & more spores/ seeds produced = potentially greater carrying capacity. In turn the animals that feed on the plants has a potentially larger carrying capacity
How does pH effect the carrying capacity of a population
It affects the action of enzymes. A population of organisms is larger where the appropriate pH exists and smaller or non-existent where the pH is different from the optimum
How does water and humidity effect the carrying capacity of a population
Areas of scarce water, populations are small and consist only of species that are well adapted to living in dry conditions.
Humidity affects the transpiration rate in plants and the evaporation of water from the bodies of animals. In dry air conditions, the population of species adapted to tolerate low humidity will be larger than those without the adaptations.
When any abiotic factor is below the optimum for a populations, what generally occurs
Fewer individuals are able to survive since their adaptations are not suited to the conditions, if no individuals have adaptations that allow survival, the population becomes extinct
What is intraspecific competition
Competition that occurs when individuals of the same species compete with one another for resources such as food, water, breeding, sites, etc.
If the availability of resources is great, what does that mean for the population
The larger the population
What is interspecific competition
It occurs when individuals of different species compete for resources such as food, light, water, etc.
What is known as the competitive exclusion principle
When there is the complete removal of one species, due to competition
What does the competitive exclusion principle state
That where 2 species are competing for limited resources, the one that uses these resources most effectively will ultimately eliminate the other.
What is a predator
An organism that feeds on another organism, known as their prey
What is the effect of predator-prey relationship on population size
- Predators eat the prey = reducing prey populations size
- Fewer prey means more competition between the predators
- Reduced predator population since some are unable to obtain enough prey to survive or to reproduce
- Fewer predators means less prey eaten so more survive and are able to reproduce
- Prey population increases
- More prey= more food for predators so predator population increases
Name other reasons for cyclic fluctuation in populations, other than predator-prey relationships
- Disease
- Climatic factors
Why is it important for a population to experience crashes from predators, disease or climatic factors
It causes selection pressure, meaning those that can withstand these adverse conditions are more likely to survive and reproduce - so the population evolves to be better adapted to the prevailing conditions
What are the 2 sampling techniques used in the study of habitats
- random sampling using frame quadrats or point quadrats
- systematic sampling along a belt transect
Why is avoiding bias when sampling good
Avoiding bias by sampling randomly ensures that the data obtained are reliable
What are the 3 main steps when sampling at random
- Lay out 2 long tape measures at right angles, along 2 sides of the study area
- Obtain a series of coordinates by using random numbers taken from a random number generator
- Place quadrat at the intersection of each pair of coordinates and record the species within it
When would a systematic sample be better than a random sample
Where there’s some form of gradual change in the communities of plants and animals takes place.
What is meant by the word abundance
The number of individuals of a species within a given area
What is the minimum number of quadrat that must be used in an experiment to obtain reliable data
20
Describe the mark-release-recapture method
A known number of animals are caught, marked, and then released back into the community. Later, a given number of individuals is collected randomly and the number of marked individuals is recorded.
What is the equation for the mark-release-recapture method
estimated population size = (total number of individuals in the first sample x the total number of individuals in the second sample) / number of marked individuals recaptured
Name assumptions the mark-release-recapture method relies on
- The proportion of marked to unmarked in the second sample is the same as the proportion in the population as a whole
- The marked individuals released distribute themselves evenly amongst the rest of the population
- No immigration into or emigration out of the population
- There are few if any deaths or births
- The method of marking is not toxic, nor make the individual more liable to predation
- The mark doesn’t rub off
What does the term succession describe
Describes the changes, over time, in the species that occupy a particular area
Succession takes place in a series of stages. At each stage new species colonise the area and these may change the environment. How may these species later change the environment?
- Making it less suitable for the existing species. As a result the new species may out-compete the existing one and so take over a given area
- Making it more suitable for other species with different adaptations. As a result this species may be out-competed by the better adapted new species
What is the name for the organisms that are involved in the first stage of succession that colonise an inhospitable environment
Pioneer species
What’s the name of the community that the pioneer species create
Pioneer community
Name some features of a pioneer species that suits them to colonise
- Asexual reproduction, so a single organism can rapidly multiply to build up a population
- The production of vast quantities of wind-dispersed seeds or spores so they can easily reach isolated situations
- Rapid germination of seeds
- The ability to photosynthesis - not dependent on animal species
- The ability to fix nitrogen from atmosphere - soil has little to no nutrients
- Tolerance to extreme conditions
What is a climax community
When the community is in a stable state and comprises a balanced equilibrium of species with few, if any, new species replacing those that have become established - in this state many species flourish and there is much biodiversity
During an succession there are a number of common features that emerge, what are they ?
- The abiotic environment becomes less hostile
- A greater number and variety of habitats and niches
- Increased biodiversity
- More complex food webs
- Increased biomass
What determines the dominant species in a climax community
Abiotic factors like climate
Why does the secondary succession occur more rapidly
Because the soil already exists in which spores and seeds often remain alive in the soil, and there is an influx of animal and plants through dispersal and migration from the surrounding area
In the secondary succession, will all of the species in the climax community be the same as the first climax community and why
NO, because the land has been altered in some way, e.g. by fire, so some of the species in the climax community will be different
What is conservation
The management of the Earth’s natural resources by humans in such a way that maximum use of them can be made in the future.
When human conserve, what 2 things are they maintaining
- Ecosystems
- Biodiversity
What are the main reasons for conservation
- Personal
- Ethical
- Economical
- Cultural and aesthetic
Explain the personal reason for conservation
To maintain our planet and therefore our life support system
Explain the ethical reason for conservation
Other species have occupied the Earth far longer than we have and should be allowed to coexist with us. Respect fro living things is preferable to disregard for them
Explain the economic reason for conservation
Living organisms contain a gigantic pool of genes with the capacity to make millions of substances, many of which may prove valuable in the future. Long-term productivity is greater if ecosystems are maintained in their natural balanced state.
Explain the cultural and aesthetic reason for conservation
Habitats and organisms enrich our lives. Their variety adds interest to everyday life and inspires writer, poets, artists, composers, and others who entertain and fulfill us
Name 2 methods of conservation used in moorlands to prevent a climax community
- Grazing
- Burning of heather
Loss of nutrients into Lake Malawi has resulted in a decrease in some fish populations, explain why (4 marks)
-Growth/increase of algae/ surface plants/ algal bloom blocks light
- Reduced photosynthesis so plants die
- Saprobiotic organisms respire aerobically
- Less oxygen for fish to respire
The mark-release-recapture method can be used to estimate the size of a fish population, explain how (4 marks)
- Capture sample, mark and release
- Ensure marking is not harmful
- Allow time for fish to randomly distribute before collecting second sample
- Population= number in first sample x number in second sample divided by the number of marked fish in second sample
Succession occurs in natural ecosystems, Describe and explain how succession occurs (4 marks )
- Colonisation by pioneer species
- Pioneer species change environment factors
- Environment becomes more hostile for new species
- Increase in biodiversity
- TO climax community
Describe how you could estimate the size of a population of sundews in a small marsh (5 marks)
- Use a grid / use tape measures
- Method of obtaining random coordinates / random number generator
- Count number in a quadrat
- Use 30 quadrats and calculate mean number per quadrat
- Mean number of plants per quadrat multiplied by number of quadrats in marsh
