C4. Succession Flashcards
What is succession?
Ecosystems are _____________-they’re constantly changing. Succession is the process by which an ecosystem changes over time. Succession happens in a series of stages. At each stage, the plant and animal communities in an area slowly change the environmental conditions (for example, by making the soil more fertile), making the conditions more suitable for other species with different adaptations. This means that the biotic conditions change as the abiotic conditions change, causing one ____________of organisms to be succeeded (replaced) by another.
What is succession?
Ecosystems are dynamic-they’re constantly changing. Succession is the process by which an ecosystem changes over time. Succession happens in a series of stages. At each stage, the plant and animal communities in an area slowly change the environmental conditions (for example, by making the soil more fertile), making the conditions more suitable for other species with different adaptations. This means that the biotic conditions change as the abiotic conditions change, causing one community of organisms to be succeeded (replaced) by another.
Primary succession
Primary succession happens on land that’s been newly formed or exposed, e.g. where a volcano has erupted to form a new rock surface, or where sea level has dropped, exposing a new area of land. There’s no soil or organic material to start with, i.e. just bare rock.
Primary succession happens on land that’s been newly formed or exposed, e.g. where a volcano has erupted to form a new rock surface, or where sea level has dropped, exposing a new area of land. There’s no soil or organic material to start with, i.e. just bare rock.
Primary succession - 1. Pioneer stage of succession
Primary succession starts when species ___________a new land surface. ________and _________are blown in by the ______and begin to grow. The first species to colonise the area are called _________ ________. The ________ ___________are _________(________) and only pioneer species can grow because they’re specially adapted to cope with the harsh conditions.
Primary succession starts when species colonise a new land surface. Seeds and spores are blown in by the wind and begin to grow. The first species to colonise the area are called pioneer species. The abiotic conditions are hostile (harsh) and only pioneer species can grow because they’re specially adapted to cope with the harsh conditions.
Primary succession - 2. Pioneer species change the abiotic conditions - they ___and microorganisms _______________the dead organic material (humus), which forms a basic ____. This makes conditions _____ _________, e.g. the basic soil helps to retain water, so new organisms with different adaptations can move in and ______.
Pioneer species change the abiotic conditions - they die and microorganisms decompose the dead organic material (humus), which forms a basic soil. This makes conditions less hostile, e.g. the basic soil helps to retain water, so new organisms with different adaptations can move in and grow.
Primary succesion - 3. The new organisms then ____and are ______________, adding more __________ __________, making the soil deeper and richer in minerals such as ________. Nitrogen-fixing bacteria turn nitrogen from the atmosphere into ammonia. This forms ammonium ions in solution that can then be used by plants. This means larger plants like ________can start to grow in the deeper soil, which retains even more _______and contains more nutrients.
Some new species may change the environment so that it becomes less suitable for the previous species. For example, sand sedge stabilises the sand through the growth of rhizomes (underground stems). This makes the conditions less suitable for marram grass, which needs constant reburial by sand in order to grow healthily.
The new organisms then die and are decomposed, adding more organic material, making the soil deeper and richer in minerals such as nitrates. Nitrogen-fixing bacteria turn nitrogen from the atmosphere into ammonia. This forms ammonium ions in solution that can then be used by plants. This means larger plants like shrubs can start to grow in the deeper soil, which retains even more water and contains more nutrients.
Some new species may change the environment so that it becomes less suitable for the previous species. For example, sand sedge stabilises the sand through the growth of rhizomes (underground stems). This makes the conditions less suitable for marram grass, which needs constant reburial by sand in order to grow healthily.
Primary succession - 4. Later stages of succession
At each stage, different _______and _________that are better adapted for the improved conditions move in, out-compete the ______and ______that are already there, and become the ___________ ________in the ___________. The dominant species are the ones which cause the most change to the abiotic environment, making it more suitable for other species.
As succession goes on, the ecosystem becomes more _________. _____ __________ _____ __ alongside existing species, which means that ______________increases. Plants create more habitats for animals, the abiotic conditions become ____ _________and the amount of biomass ___________.
At each stage, different plants and animals that are better adapted for the improved conditions move in, out-compete the plants and animals that are already there, and become the dominant species in the ecosystem. The dominant species are the ones which cause the most change to the abiotic environment, making it more suitable for other species.
As succession goes on, the ecosystem becomes more complex. New species move in alongside existing species, which means that biodiversity increases. Plants create more habitats for animals, the abiotic conditions become less hostile and the amount of biomass increases.
Primary succession - 5. Climax community
Eventually these changes result in a _______ _____________-the ecosystem is supporting the largest and most complex community of plants and animals it can. It won’t change much more—it’s in a ______state.
Eventually these changes result in a climax community-the ecosystem is supporting the largest and most complex community of plants and animals it can. It won’t change much more—it’s in a steady state.
Primary Succession example
Secondary succession
Secondary succession happens on land that’s been _________of all the ______, but where the ____remains, e.g. after a forest ___or where a forest has been cut down by humans. The established community of _______is usually ___________, but without too much disturbance to the soil. It can occur during any stage (including the climax community) after the pioneer stage.
The process of secondary succession is similar to primary succession, but because there’s already a soil layer, secondary succession starts at a later stage-and the pioneer species are larger plants, eg, _______.
Secondary succession happens on land that’s been cleared of all the plants, but where the soil remains, e.g. after a forest fire or where a forest has been cut down by humans. The established community of species is usually destroyed, but without too much disturbance to the soil. It can occur during any stage (including the climax community) after the pioneer stage.
The process of secondary succession is similar to primary succession, but because there’s already a soil layer, secondary succession starts at a later stage-and the pioneer species are larger plants, eg, shrubs.
Human impacts on succession
Human activities can prevent succession, stopping a climax community from developing. When succession is stopped artificially like this the climax community is called a ______________.
Human activities can prevent succession, stopping a climax community from developing. When succession is stopped artificially like this the climax community is called a plagioclimax.
Climatic climax communities
Which species make up the climax community depends on what the climate’s like in an ecosystem. The climax community for a particular climate is called its _________ _______.
Which species make up the climax community depends on what the climate’s like in an ecosystem. The climax community for a particular climate is called its climatic climax.
Tip: The main difference between the two types of succession is that _____is present at the start of secondary succession but not in primary succession. Secondary succession therefore tends to reach the climax community
more quickly as a result.
Tip: The main difference between the two types of succession is that soil is present at the start of secondary succession but not in primary succession. Secondary succession therefore tends to reach the climax community
more quickly as a result.
