Genetics, Populations, Evolution and Ecosystems - Populations in Ecosystems Flashcards
What is ecology?
The study of the inter-relationships between organisms and their environment. The environment includes both non-living (abiotic) factors, e.g. temperature and rainfall, and living (biotic) factors, e.g. competition and predation.
What is an ecosystem?
A biological community of interacting organisms and their physical environment. Ecosystems can range in size from very small to very large.
What two major processes within an ecosystem are there to consider?
- the flow of energy through the system
- the cycling of elements within the system
What is a population?
A population is a group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed.
What is the carrying capacity?
An ecosystem supports a certain size of population of a species called the carrying capacity.
Why can the size of a population vary as a result of?
- the effect of abiotic factors
- interactions between organisms (e.g. intraspecific and interspecific competition and predation)
What is a community?
All the populations of different species living and interacting in a particular place at the same time.
Where are organisms found?
In places where the local environmental conditions fall within the range that their adaptations enable them to cope with.
What is a habitat?
A habitat is the place where an organism normally lives and is characterised by physical conditions and the other types of organisms present. Within an ecosystem, there are many habitats.
What are microhabitats?
Within each habitat there are smaller units, each with their own microclimate. These are called microhabitats.
What is an ecological niche?
A niche describes how an organism fits into the environment. A niche refers to where an organism lives and what it does there. It includes all the biotic and abiotic conditions to which an organism is adapted in order to survive, reproduce and maintain a viable population.
Can two species occupy the same niche?
Some species may appear very similar, but their nesting habits or other aspects of their behaviour will be different, or they may show different levels of tolerance to environmental factors. No two species occupy exactly the same niche. This is known as the competitive exclusion principle.
What is the population size?
A population is a group of individuals of the same species that occupy a habitat at the same time. The number of individuals in a population is the population size. Populations are dynamic in that they vary in size and composition over time.
When are logarithmic scales usually used?
to represent the number of bacteria (when measuring the growth of microorganisms)
What is the size of any population eventually determined by?
a limiting factor
What are 4 abiotic factors?
A species can only live within a certain range of abiotic factors and this range differs from species to species. The abiotic conditions that influence the size of a population include:
- temperature
- light
- pH
- water and humidity
How is temperature an abiotic factor?
Each species has a different optimum temperature at which it is best able to survive. The further away from this optimum, the fewer individuals in a population are able to survive and the smaller is the population that can be supported.
How does temperature affect cold-blooded animals and plants?
In plants and cold-blooded animals, as temperatures fall below the optimum, the enzymes work more slowly and so their metabolic rate is reduced. Populations therefore have a smaller carrying capacity.
At temperatures above the optimum, the enzymes work less efficiently because they gradually undergo denaturation. Again, the population’s carrying capacity is reduced.
How does temperature affect warm-blooded animals?
The warm-blooded animals can maintain a relatively constant body temperature regardless of the external temperature. However, the further the temperature of the external environment gets from their optimum temperature, the more energy these organisms expend in trying to maintain their normal body temperature. This leaves less energy for individual growth and so they mature more slowly and their reproductive rate slows. The carrying capacity of the population is therefore reduced.
How is light an abiotic factor?
As the ultimate source of energy for most ecosystems, light is a basic necessity of life. The rate of photosynthesis increases as light intensity increases. The greater the rate of photosynthesis, the faster plants grow and the more spores or seeds they produce. Their carrying capacity is therefore potentially greater. In turn, the carrying capacity of animals that feed on plants is potentially larger.
How is pH an abiotic factor?
This affects the action of enzymes. Each enzyme has an optimum pH at which it operates most effectively. 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 is water and humidity an abiotic factor?
Where water is scarce, populations are small and consist only of species that are well adapted to living in dry conditions. Humidity affects the transpiration rates in plants and the evaporation of water from the bodies of animals. Again, in the dry air conditions, the populations of species adapted to tolerate low humidity will be larger than those with no such adaptations.
In terms of abiotic factors, why do populations become extinct?
Generally, when any abiotic factor is below the optimum for a population, fewer individuals are able to survive because their adaptations are not suited to the conditions. If no individuals have adaptations that allow survival, the population becomes extinct.
