Species and Populations Flashcards
What is a species?
A species is a group of organisms (living things) sharing common characteristics that interbreed and produce fertile offspring
What is a population?
A population is a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding
What is a habitat?
A habitat is the environment in which a species normally lives
Three factors affect population size:
- Natality (birth rate)
- Mortality (death rate)
- Migration (immigration and emigration)
What are abiotic factors?
Abiotic factors are the non-living, physical factors that influence the organisms and ecosystem
e.g. temperature, sunlight, pH, salinity and pollutants
What are biotic factors?
Biotic factors are the living components of an ecosystem - organisms, their interactions or their waste - that directly or indirectly affect another organism
What is a niche
A niche describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds
What is a fundamental niche?
Fundamental niche describes the full range of conditions and resources in which a species could survive + reproduce
What is a realised niche?
Realised niche described the actual conditions and resources in which a species exists due to biotic interactions
Name 4 biotic factors in a niche
- every relationship that organism may have
- where it lives
- how it responds to resources available, to predators, to competition
- how it alters these biotic factors
Name 2 abiotic factors in a niche
- how much space there is
- availability of light, water etc..
Can two species inhabit the same ecological niche in the same place at the same time?
No two species can inhabit the same ecological niche in the same place at the same time.
If many species live together they must have slightly different needs and responses so are not in the same niche
e.g. Lions and cheetahs live in same area of African savannah but lions hunt bigger herbivores e.g. zebras whereas cheetahs hunt smaller herbivores e.g. impalas
What are limiting factors?
Limiting factors are factors which slow down growth of a population as it reaches its carrying capacity
Give 2 examples of limiting factors that restrict the growth of populations in nature
- Phosphate being in limited supply in most aquatic systems
- Low temperature in tundra which freezes the soil + limits water availability to plants
What is the carrying capacity?
Carrying capacity is the maximum number of species or ‘load’ that can be sustainably supported by a given area
What is population dynamics?
Population dynamics is the study of factors that cause changes to population sizes
When does competition take place?
All organisms in any ecosystem have some effect on every other organism in that ecosystem
Any resource in any ecosystem exists only in a limited supply
When these 2 conditions apply jointly, competition takes place
What is intraspecific competition?
- Intraspecific competition is between members of the same species.
- When the numbers of a population are small, there is little competition between individuals for resources
- Provided individuals can find mates, population growth will be high
Give an example of intraspecific competition (negative feedback mechanism)
- POPULATION FALLS (leads to)
- Decrease comp. for good nesting sites
- Increased no. eggs hatch successfully
- Birth rate increases
- POPULATION GROWS
- Increased comp. for good nesting sites
- Decreased no. eggs hatch successfully
- Birth rate decreases
- POPULATION FALLS
What does intraspecific competition tend to do?
Intraspecific competition tends to stabilise population numbers . It produces an S-shaped curve
Name 1 way species deal with intraspecific competition
By being territorial e.g. deer
Individual / pair holds an area + fends off rivals
Individuals that are most successful reproductively will hold biggest territories + hence have access to more resources so will be more successful at breeding
What is interspecific competition?
- Individuals of different species competing for same resource
- May result in a balance, in which both species share resource
- One-species may totally out-compete the other (COMPETITIVE EXCLUSION)
Give an example of both interspecific competition + competitive exclusion
A garden has become overrun by weeds. A number of weeds coexist together, but often the original domestic plants have been totally excluded
Why does competition reduce the carrying capacity for each of the competing species?
Competition reduces the carrying capacity for each of the competing species, as both species use the same resource(s)
