populations Flashcards
what is a species
a group of similar organisms (physical,characteristically behaviourally) that can reproduce to produce fertile offspring
how can two organisms not successfully interbreed to produce fertile offspring
have a different diploid number of chromosomes in their cells
eg
a horse has 64 chromosomes in its cells while a donkey has 62. When the haploid gametes from a horse (32) and a donkey (31) combine, the resulting zygote has 63 chromosomes
Cells that have an odd number of chromosomes are not viable. The chromosomes can not form homologous pairs during meiosis to produce gametes
how do biologists define a species
Similarities/differences in observable features (morphology)
Similarities/differences in DNA
Similarities/differences in RNA
Similarities/differences in proteins
The ability to interbreed and produce fertile offspring
then place into categories
what is a population
group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed to produce fertile offspring
do populations vary in size
yes,
it is often dependent on the environment and abiotic/biotic factors
eg
The Amur leopard (Panthera pardus orientalis), now found only in the Amur River basin of eastern Russia (having already gone extinct from China and the Korean Peninsula) has a remaining population of around 60 individuals
Although humans (Homo sapiens) used to live in separate populations, we are now widely considered as one global population of around 7,800,000,000 individuals
what is a community
Multiple populations (of different species) living and interacting in the same area
how do communities form ecosystems
by interacting with the non-living components of the environment
what is an ecosystem
The interaction between a community (the living, biotic part) and the non-living (abiotic) parts of the environment
-An ecosystem is a relatively self-contained community of interacting organisms and the environment they live in, and interact with
There is a flow of energy within an ecosystem and the nutrients within it are recycled (e.g. the carbon, nitrogen and phosphorus cycles)
There are both living (biotic) components and non-living (abiotic) components within an ecosystem
how do ecosystems vary
they are dynamic and constantly changing
Ecosystems vary greatly in size and scale
Both a small pond in a back garden and the open ocean could be described as ecosystems
Ecosystems vary in complexity:
A desert is a relatively simple ecosystem
A tropical rainforest is a very complex ecosystem
No ecosystem is completely self-contained as organisms from one ecosystem are often linked to organisms from another
For example, many birds species are able to migrate long distances to find food sources or breeding locations from various ecosystems
what is a niche
the role that a species plays within a habitat
including
The biotic interactions of the species (e.g. the organisms it feeds on and the organisms that feed on it)
The abiotic interactions (e.g. how much oxygen and carbon dioxide the species exchanges with the atmosphere)
what is a habitat
the place where a species lives within an ecosystem
how many species occupy a niche
one
what happens when multiple species occupy the same niche
If two species try to occupy the same niche, they will compete with each other for the same resources
One of the species will be more successful and out-compete the other species until only one species is left and the other is either forced to occupy a new, slightly different niche or to go extinct from the habitat or ecosystem altogether
what are some abiotic factors
-temperature- optimum temp - if go below reaction slow and require more energy for body temp maintenance - if go above - enzymes denature and less energy - pop growth is limited
-light - more light = more transpiration = more plants grow and increased capacity of animals feeding on plants
-ph - optimum pH - each individual has own - if go away from this then less energy
-wind and humdity
what are some biotic factors
Biotic factors can be split into three main types:
Interspecific competition
Intraspecific competition
Predation
Could also have disease
how is the pop size controlled
The maximum stable population size of a species that an ecosystem can support is known as the carrying capacity
Every individual within a species population has the potential to reproduce and have offspring which contribute to population growth
In reality, however, there are many abiotic and biotic factors that prevent every individual in a population from making it to adulthood and reproducing
This ensures the population size of each species is limited at some point (i.e. the carrying capacity of that species is reached)
describe max carrying graph
slow at start - limited pop size - so less reproduction
-due to different gestation lengths/ enzymes work out diff speeds
-rapid increase - optimum conditions
-The point at which the graph started to flatten out (plateau) is the carrying capacity of this population
At this point, the environmental (abiotic and biotic) factors that stop all individuals from surviving and reproducing result in the population no longer being able to grow in size - food availability
-decrease would be due to toxic waste production from organisms which kills them
what is interspecific competition
This is competition for the same resources between individuals from different species
In some cases, competition between species means that the sizes of both populations are limited
This can occur as each species has access to fewer resources and therefore less chance of survival and reproduction
This usually occurs if the two species are similarly well-adapted to the habitat
In other cases, competition between species can lead to a decrease in the population size of one of the species and an increase in the population size of the other
This can occur if one species is able to out-compete the other for resources and therefore has a greater chance of surviving and reproducing
This usually occurs if one of the species is better adapted to the habitat
what is intraspecific competition
This is competition for the same resources between individuals from the same species
For example:
When resources are plentiful, the population of grey squirrels increases
As the population increases, however, there are more individuals competing for these resources (e.g. food and shelter)
At some point, the resources become limiting and the population can no longer grow in size - the carrying capacity has been reached
what is predation
Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers who are themselves eaten by tertiary consumers
Consumers that kill and eat other animals are known as predators, and those eaten are known as prey
In a stable community, the numbers of predators and prey rise and fall in cycles, limiting the population sizes of both predators and prey
what are the components that make up an ecosystem
Biotic components
There is a constant flow of energy within ecosystems. For example, the process of feeding ensures that energy can move between organisms:
Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers, who are themselves eaten by tertiary consumers
When organisms die or produce waste products, the organic matter is broken down (decomposed) by organisms such as bacteria and fungi
Species numbers are constantly fluctuating within ecosystems, as populations decline (through death and emigration) or grow (through birth and immigration)
These factors mean that the population size of a particular species constantly varies around the theoretical carrying capacity depending on factors such as interspecific or intraspecific competition, geographical location and the time of year
Abiotic components
There is also a constant flow of nutrients within ecosystems as they are continually recycled (e.g. the carbon, nitrogen and phosphorus cycles)
Water is also constantly cycled in ecosystems via the water cycle
Other aspects of weather that can affect communities of species, including abiotic factors such as temperature and wind, are also very dynamic
describe and explain the predator/prey graph
-prey consistently higher than predator
-prey peaks before the predator
EXPLAIN
-predators eat their prey - so prey numbers are reduced
-fewer prey remain so there is greater competition for the food source
-predator pop is reduced as some of the population will not have enough food
-with fewer predators, prey numbers begin to increase as less of them are eaten
-more prey are then available as a food source so the numbers pf predators begin to increase again
-cycle continues
how do selective pressures affect populations
they regulate and control the numbers
what are density (no of pop) factors - PANDA
-predators
-availability of resources
-nutrient availability
-disease/pathogenic spread
-accumulation of wastes
