Biology module 4

• Population refers to the group of organisms of the same species living together in an area at the same time.
• Ecosystem includes both biotic (living) and abiotic factors (non-living).
• Abiotic factors include air temperature, rainfall, water availability, humidity and pH.
• Competition refers to when two or more populations compete for the same limited resources within the same area.
• Organisms may compete with intraspecific competition (own species) or interspecific competition (another species).
• Species/populations better suited at acquiring resources become dominant.
• Selective pressure directly affects organisms' abundance which is determined by the availability of resources.
• Competitors reduce each other's growth, surisurvivalval and reproduction which consequently limits species population and abundance.
• Mutualism is where both species involved are benefited.
• Commensalism is when one species is benefited, whilst the other is neutral (not benefited nor disadvantaged).
• Parasitism is when one species is benefited whilst the other is disadvantaged.
• Leaves on the canopy layer are smaller due to most exposure to sunlight to minimise loss of water.
• Leaves on the ground level are bigger due to less exposure to sunlight and maximising surface area to volume ratio to collect more sunlight.
• A niche is part of an ecosystem that an organism occupies which includes all resources a species use.
• An ecological niche is an important function a specific organism carries out for ecosystem.
• A realised niche is a niche organism that occupies as a result of limiting factors present in the habitat.
• The competitive exclusion principle is when two species cannot coexist in the same place if competing for the same resources.
• Carrying capacity is the maximum population size that ecosystems can sustain indefinitely for a certain species, while the species is in equilibrium (not growing or declining)
• Logistic growth is the initial exponential growth of a population.
• Logistic growth flattens out as it begins to be affected by density-dependent factors. (population may decline to equilibrium and the population remains at the carrying capacity)
• Competition between species for resources affects reproduction and survival rates.
• Symbiosis is the group of interactions in which two organisms live together in a close relationship that is beneficial to at least one of them.
• disease is any process that affects the normal functioning of an organisms' tissues/organs.
• Disease outbreaks can cause disturbance and make populations more vulnerable to extinction.
• Decrease in prey also results in decrease of predator (affect abundance of species population)
• When measuring distribution, a transect is used by measuring a large area divided into sections.
• When measuring abundance, a quadrat is used by a measured square/shape being randomly placed in a particular ecosystem.
• When measuring abundance and distribution, capture and recapture is used as traps are set and species are caught, tagged and released.
• The advantages of capture-recapture is that it is simple and easy for larger and faster-moving animals.
• The disadvantages of capture-recapture are that it is only suitable for mobile animals, is time-consuming and disturbs the environment.
• Advantages of using transects is that is quick, easy and inexpensive.
• Disadvantages of using transects is that it is only suitable for plants and stationary animals, difficult to measure and only for small populations,
• Advantages of using quadrats include being easy, inexpensive for measuring a large population and allows minimal environmental disturbance.
• Disadvantages of using quadrats include only being suitable for slower animals and plants.
• Background extinction is the steady turnover of a group of species for geological time.
• Major mass extinction is the complete disappearance of numerous species due to catastrophic event in a short period of time.
• The law of superposition is any sequence of rocks that is undisturbed, the oldest layers will be at the bottom and the youngest layers at the top.
• The law of original horizontality is all sedimentary strata are deposited horizontally to start with and only tilt or bend due to subsequent forces.
• The law of lateral continuity is that the stratum of rock will be continuous until something disturbs it (such as erosion or igneous intrusion).
• The law of cross-cutting relationships is that in any rock sequence, the layer that crosses or intrudes another is the younger rock layer.