6.3.2 Populations and Sustainability Flashcards
what is population size
the total number of organisms of one species in a habitat
why do population sizes of species vary
- because of abiotic factors
- e.g. light, water, space available
- temperature and chemical composition of surrounding
- and biotic factors
- interspecific and intraspecific competition
- predation
what happens with ideal abiotic conditions for a species
organisms can grow fast and reproduce successfully
why is ideal temperature of surroundings good for mammals
- ideal for metabolic reactions to take place
- they don’t use up as much energy maintaining body temperature
- more energy can be used for growth and reproduction
- population size will increase
what happens when abiotic conditions are not ideal for a species
organisms cannot grow fast or reproduce successfully
what happens when a mammal is facing unideal temperature of surroundings
- temperature os higher or lower than optimum body temperature
- have to use less energy to maintain right body temperature
- less energy available for growth and reproduction
- so population size decreases
what is interspecific competition
when organisms of different species compete with each other for the same resources
- e.g. grey and red squirrels competing for the same food sources and habitats in the UK
- affects resources available, and distribution of species
how does interspecific competition between two species impact resources available
- the resources available for each species is reduced
- e.g. if they share the same food source, it will be less available for both of them
- (plants compete for minerals and light)
- means that both populations are limited by a lower amount of food
- so have less energy for growth and reproduction
- so population sizes are lower in both species
- e.g. in areas where both red and grey squirrels live, both populations are smaller than if only one species was there
why does interspecific competition affect the distribution of a species
- if two species are competing
- but one is better adapted to its surroundings than the other
- the less well adapted species is out-competed
- so won’t be able to exist alongside better adapted species
- e.g. since grey squirrels have been introduced in the UK, the native red have disappeared from large areas (grey has better chance of survival as is larger so can store more fat over winter
what is intraspecific competition
organisms of the same species compete with each other for the same resources
explain how intraspecific competition occurs
1) when resources are plentiful, the population of a species increases
2) as the population increases, the number of organisms competing for the same amount of space and food increases
3) eventually, space and food will become limiting, as there isn’t enough for all the organisms
4) the population begins to decline
5) the smaller population means that there is less competition for space and food, so it is better for growth and reproduction
6) this means the population grows again
7) the maximum stable population size of a species that any ecosystem can support is called the carrying capacity
what is carrying capacity
the maximum stable population size of a species that any ecosystem can support
how would you show intraspecific competition graphically
- graph continuously oscillates
- line going through the middle horizontally shows the carrying capacity
what is predation
an organism (the predator) kills and eats (predates on) another organism (the prey)
what are predator prey populations controlled by
negative feedback
explain the negative feedback cycle of predator prey populations
1) as prey population increases, more food for the predators, so the predator populations grows
2) as the predator population increases, more prey is eaten, so the prey population begins to fall
- NEGATIVE FEEDBACK: as the prey population is restored to a more stable size
3) this means that there is less food for the predators, so their population decreases (more negative feedback)
what are the limits to using predator-prey relationships
- usually more complicated
- as other factors involved
- e.g. the population of the prey might begin to decrease initially because there were too many for the amount of food available, and predation just accelerated this decrease
what are the limiting factors of populations
factors that stop the population size of a species from increasing:
1) ABIOTIC: the amount of shelter in an ecosystem limits the population size of the species because there is only enough shelter for a certain number of individuals
2) BIOTIC: interspecific competitions limits the population size because the amount of resources available for the species decreases
- DETERMINE THE CARRYING CAPACITY OF AN ECOSYSTEM
