Chapter 19 Populations in Ecosystems Flashcards
Define species.
The ecological species concept is a concept of species in which a species is a set of organisms adapted to a particular set of resources, called a niche, in the environment.
A biological species is a group of organisms that can reproduce with one another in nature and produce fertile offspring.
Define population
A population is a group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.
Define community
A community is a group or association of populations of two or more different species occupying the same geographical area at the same time.
Define habitat
A habitat (which is Latin for “it inhabits”) is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism.
Define niche
An organism’s role in an ecosystem. Their niche is governed by adaptation to both abiotic and biotic conditions.
Define ecosystem
A community of living organisms in conjunction with the non-living components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Example: Forest
What does ‘limiting factor’ mean when talking about populations?
A factor which would limit the growth of a population.
Give 4 biotic factors.
Predation
Competition
Disease
Food availability
Give examples of 5 abiotic conditions that could limit a population.
Temperature
Light intensity
pH
Soil moisture
Wind speed
Humidity.
What is an organism’s niche?
The role taken by a type of organism within its community. This includes where it lives, feeds, what it eats, what eats it.
Why is it important that species occupy different niches?
This reduces competition and increases the survival rate of both species.
Give an example of two similar species and how they adapted to occupy different niches.
- Swifts and pipistrelle bats - hunt at different times.
- Different species of warblers - adapted to different temperatures and light intensities and live in different layers of the tree.
(see more in the Booklet)
In what ways can niches differ?
Niches include biotic and abiotic factors and can be separated by time, location or behaviour.
What is the problem with trying to demonstrate niche separation artificially?
The number of variables are very high and you can never replicate a proper ecosystem. Taking away variables does not mean you are controlling them and if these are influential, they might change your results.
What is an adaptation and how do they occur?
An adaptation is a feature that members of the same species have that increases their chance of survival and reproduction in their habitat. Occur through natural selection: Organisms in a species with better adaptations to their environment are more likely to survive and reproduce and pass on the alleles that code for these adaptations – this increases the frequency of these alleles in the population.
What is the carrying capacity of a habitat?
The carrying capacity of a habitat is the number of a particular species which can be supported without environmental degradation.
What does a carrying capacity graph look like?
Describe the steps in the predator-prey relationship.
- Prey increase in number so more food is available for predators
- Predator numbers increase
- Predators eat more of the prey
- Prey numbers decrease
- Less food for predators
- Predator number then decrease
- This causes an increase in prey numbers and cycle repeats with a slight time lag between prey and predator events.
Besides predator prey interactions, what else can cause fluctuations in populations?
The effect of abiotic factors.
Biotic factors such as inter and intraspecific competition.
How do changes in abiotic and biotic factors affect evolution?
They create a selection pressure. This means that the best adapted survive to reproduce.
Define interspecific competition.
Interspecific competition occurs between organisms of different species.
Define intraspecific competition.
Intraspecific competition occurs amongst members of the same species.
Which type of competition is the most intense and why?
Intraspecific competition is the most intense because individuals are competing for exactly the same resources.
Without using a semi-log sale what shape would the growth curve for microorganisms be?
Sigmoid.
Using a semi-log scale what shape would the growth curve for microorganisms be?
Name the 4 phases in the growth of microorganisms.
Lag phase
Log phase
Stationary phase
Death phase
Name the two main types of quadrat.
Point and frame quadrats.
How do you sample randomly?
- Lay out 2 tape measures at right angles
- Use a random number generator to produce coordinates
- Place the quadrat at the coordinate intersection.
What is succession?
Succession is how an ecosystem changes over time. At each stage of succession certain species may be recognised which change the environment so that it becomes more suitable for other species with different adaptations. The new species may change the environment in such a way that it becomes less suitable for the previous species.
Changes that organisms produce in their abiotic environment can result in a less hostile environment and change biodiversity.
