3.7- Chapter 19- Populations in Ecosystems Flashcards
What factors affect populations and communities?
- Competition for survival occurs between and within populations.
- Populations within communities are affected by biotic (competition, predation) and abiotic (temperature, rainfall) factors in an ecosystem.
What are ecosystems?
Dynamic systems made up of a community and non-living factors. e.g. a pond.
Describe the features of ecosystems?
- There is little to no net loss or gain between natural ecosystems- most substances are recycled.
- Can be very large to very small
What major process occur in ecosystems?
- The flow of energy through the system- energy is transferred.
- The recycling of elements within the system.
What is a community?
- Populations of different species form a community.
- All the populations of different species living together and interacting at a particular place at the same time.
What is a population?
A group of individuals of one species that occupy the same habitat at the same time and can potentially interbreed.
Why is a population often difficult to measure or define?
- The boundaries of a population are often difficult to define.
- Populations are dynamic and vary in size and composition over time.
What is the carrying capacity?
- The size of population of a species an ecosystem supports.
- This size in population can be sustained over a relatively long period.
- Determined by limiting factors.
Why do population sizes vary?
- Due to the effect of abiotic factors
- Due to interactions between organisms- interspecific and intraspecific competition and predation.
What is a habitat?
- The place where an organism normally lives.
- Characterised by physical conditions and other types of organisms present.
- Within an ecosystem there are many habitats.
What are microhabitats?
- Smaller units within habitats with their own microclimate.
- e.g. mud at the bottom of the stream- microhabitats for bloodworms.
What is an ecological niche?
- Within a habitat, a species occupies a niche governed by adaptation to both abiotic and biotic conditions.
- The niche describes how the organism is adapted to its environment to survive reproduce, and maintain a viable population..
- The niche includes where an organism lives and what it does there.
- Some species may appear very similar but their behaviour may be different due to different levels of tolerence to environmental factors.
What is the competitive exclusion principle?
No two species can occupy the same niche- the competition means one will not be able to outcompete the other and will die out.
When is it possible/ not possible to plot a population growth curve?
- Where a population grows in size slowly- can plot a graph of population against time.
- Rapid population in short period of time- hard to plot growth curve e.g. micro-organisms.
How can we mitigate the large population size differences in the population growth of bacteria?
Use a logarithimic scale- easier to see patterns.
What is the population size?
The number of individuals in a population.
How does population size vary in a population growth curve of photosynthetic bacteria.
- Initially when there are good conditions, the population increases rapidly because all the factors needed for growth are persent and there is no limiting factors.
- Over time, more nutrients are consumed as the population becomes larger, the population becomes so large the bacteria prevent light reaching those at lower levels, other species may be introduced and compete for the same resources as the bacteria or predate on bacteria, and wintery conditions may bring lower light intensity, making conditions tought.
- The growth of hte population slows and then stops.
- The population size sometimes then decreases
- The population then reaches a constant size until conditions change and factors improve to increase growth again.
What affects population size?
- Many biotic and abiotic factors.
- Changes in these factors influence the rate of growth and size of the population.
Why does no population grow indefinitely?
- Factors limit growth- e.g. food, water etc.
- Accumulation of toxic wastes, disease and predators limit growth.
- The population stays within the carrying capacity of its ecosystem.
Name the main abiotic factors that can affect population growth.
- Temperature
- Light
- pH
- Water and humidity
How does temperature affect population size?
- Each species has a different optimum temperature where it survives best
- Further from optimum= few individuals are able to survie= smaller population.
- Especially affects plants and cold-blooded animals- if fall below optimum- enzymes work more slowly- metablic rate reduced- smaller carrying capacity.
- Above optimum- enzymes work less efficiently and denature- carrying capacity and population size reduced.
How do changes in temperature affect warm-blooded animals?
- Warm blooded animals- birds and mammals- maintain constant body temperature regardless of external temperature.
- Extreme temperature changes from the optimum- mean more energy expended trying to maintain normal body temperature.
- Less energy for individual growth- mature more slowly and reproductive rate slows.
- Carrying capacity and population size reduced.
How does light impact population size?
- Light is the main source of energy for most ecosystems- basic necessity of life.
- Rate of photosynthesis increases as light intensity increases.
- Faster photosynthesis= faster plant growth and more seeds.
- Carrying capacity greater and carrying capacity of animals that feed on the plants greater.
How does pH impact population size?
- Affects the action of enzymes.
- Enzymes- have optimum pH where work most effectively.
- Population of organisms larger where the right pH exists and smaller where pH is different from the optumum.
