Ecosystems- Topic 10 Flashcards
Interspecific competition
Competition between different species in a community for the same resources.
Effect of interspecific competition
Reduce abundance of the competing species. If there is a greater density of one species or it has a faster reproduction rate then the other species may become locally extinct.
Intraspecific competition
Competition between the same species for limited resources
Effects of intraspecific competition
Some individuals may not survive or reproduce causing population growth to slow. This strengthens the population through natural selection.
What is an autotroph?
An organism that can make its own organic molecules from inorganic molecules
What is a heterotroph?
An organism that derived its nutritional requirements from organic substances
What is succession?
Directional change in an ecosystem over time to form a climax community
Primary succession
When organisms colonise a lifeless habitat
Secondary succession
When organisms re-colonise a devastated ecosystem (there is still some life)
What is the role of pioneer species?
Stabilise, add nutrients which riches the ground and add humus (organic matter)
What are 5 seres of primary succession
Sere 1: empty habitat- harsh environment
Sere 2: habitat colonised by pioneer species
Sere 3: pioneer species will modify the environment creating conditions that support new species
Sere 4: new plant species increases diversity- various animals enter habitat. The early species are replaced by new species.
Sere 5: a climax community.
Structure of lichens
Composed of fungus and algal cells.
the algal cells photosynthesise and the fungus secretes enzymes to break down food which it then reabsorbs.
Primary succession of bare rock
Bare rock has minerals but lack of soil and water
Lichens are pioneer species that are the primary colonisers of bare rock.
When these die humus is added forming soil which begins the growth of a new community that outcompetes lichens.
Quantifying populations: size
Number of individuals in a population
Quantifying populations: density
Number of individuals per unit area
Quantifying populations: growth rate
The changes in the number of individuals per unit time
Growth of populations: 1
LAG PHASE
initial population growth rate is slow due to individuals being widely dispersed
Growth of populations: 2
LOG GROWTH
population grows at its maximum possible rate- birth rate is higher than death rate
(Biotic potential)
What is biotic potential and what is it determined by?
The ability of a population to increase under ideal conditions. It is determined by rate of reproduction and size or litter
Growth of populations: 3
TRANSITION PHASE
Environmental resistance increases- increased competition increases death rate- growth rate slows
Growth of populations: 4
PLATEAU PHASE
Population reaches the maximum size that it’s ecosystem can sustain. This is the carrying capacity (k). Population now remains roughly stable
What does destruction go part of the ecosystem do to population size
Drops below carrying capacity
What is a density dependent factor?
As the population increases the limiting factor becomes a problem and impacts the community eg. Competition for food, disease
What is a density independent factor?
Remains constant regardless of population size eg: rainfall, temp
How do you calculate population growth rate?
Population at end of period - population at start of period
—————times 100
Population at start of period
Describe a predator prey interaction diagram
- Peaks of prey should be higher than peaks of predator
- troughs of predator lower than troughs of prey
- Predator to the right prey to the left
Why are the predator prey interaction diagrams rare
Most predators have multiple prey species
How will density independent factors affect the distribution of organisms?
- May need to move/migrate
2. Could limit distribution because only one area is suitable
As succession progresses what 4 things increase?
- Habitats and niches
- Biodiversity
- Complex food webs
- Biomass
What is deflected succession?
A pause in succession eg. Agriculture, grazing, pesticide
What is ACFOR?
Abundant Common Frequent Often Rare
What does the null hypothesis state?
Any differences between data sets are due to chance alone- no link
