biology b16 - adaptations, interdependence and competition

the levels of organisation within an ecosystem?

habitat - the environment in which an organism lives

population - the total number of organisms of the same species, living in the same geographical area

community - the populations of all the different species living in the same habitat

ecosystem - both the biotic and abiotic parts of an environment and how they interact

stable communities & the importance of interdependence within a community?

• within a community, each species is dependant on others for food, shelter, pollination, seed dispersal etc.

• if one species is removed from a community, it can have a major effect on the entire community

• this idea is known as interdependence

• a stable community is one where all the species & environmental factors are in balance, so that population sizes remain fairly constant

why do plants and animals compete with one another?

to survive and reproduce, organism require a supply of materials from their surroundings and from the other living organisms there, which are often in limited supply:

• plants compete with each other for light and space, and water and mineral ions from the soil

• animals often compete with each other for food, water, territory and mates

what are biotic factors?

• biotic factors are living elements of an ecosystem, such as plants and animals

• the 4 main biotic factors are:

  • availability of food - organisms successfully breed when there is plenty of food, but struggle to survive otherwise and often do not breed. so if the availability of food falls, the number of organisms in a community will also fall

  • new predators arriving - this can cause the population of prey species to fall; new predators can also outcompete existing predators which are competing for the same prey

  • one species outcompeting another - if a species is outcompeted its population may fall so much that its numbers are no longer sufficient to breed, and the species may face extinction

  • new pathogens - if an infectious disease emerges and spreads, it can wipe out a population of species

what are abiotic factors?

• abiotic factors are the non - living elements of an ecosystem

• the 7 main abiotic factors are:

  • light intensity - majorly affects plants as they all require light to carry out photosynthesis; if light intensity is too low, the rate of photosynthesis falls and plants will grow more slowly, which can have a major impact on a community (animals which feed on plants may not have enough food)

  • temperature - if the temperature of an environment changes, it could affect the distribution of species; animals could migrate and plants could disappear from some areas

  • water/moisture levels - both plants and animals require water to survive; many species are adapted to deal with low levels of water

  • soil pH and mineral content - plants may struggle to grow on soil which is too acidic/alkaline, and plants require certain minerals in the soil, such as nitrate ions for growth

  • wind intensity and direction - strong inland winds can cause plants to lose water; plants growing in sand dunes are often adapted to reduce water loss

  • carbon dioxide levels (plants) - needed for photosynthesis, so if levels fall, the rate of photosynthesis may also decrease

  • oxygen levels (aquatic animals) - oxygen is needed for aerobic respiration; while levels of oxygen in the air remain fairly constant, the level of dissolved oxygen in water can fall on hot days, which is harmful to aquatic organisms

what are adaptations and why are they important?

• adaptations are features of organisms that enable them to survive in the conditions in which they normally live. adaptations may be structural, behavioural or functional:

• structural adaptations are adaptations of body shape and or structure

• functional adaptations are adaptations to the body functions of an organism

• behavioural adaptations are adaptations to the animal’s behaviour and lifestyle (e.g being nocturnal)

some general adaptation examples?

• small body parts/curled leaves/similar reduces water/heat loss to environment → REDUCE SA

• fur can act as a camouflage, which protects from predators

• fur provides insulation & reduces heat loss

• producing dry faeces and concentrated urine reduces water loss

• being nocturnal helps avoid the heat of daytime

• spikes/thorns act as protection from predators

• extensive and shallow roots allow for maximum water uptake

• water stores in stems/tissues allow plants to survive for months w/out rain

• sharp teeth for grinding bones and tearing flesh

what are extremophiles?

• extremophiles are organisms which are adapted to live in extreme environments, such as high temperatures, pressures or salt concentrations

• bacteria living in deep sea vents are extremophiles

required practical 9 - field investigation - part A - estimating population size

• use a random number generator to obtain 2 numbers, which will be used as coordinates to find a location along two tape measures, 20m in length, set up vertically and horizontally, at a right angle to each other in the sampling area

• set down a frame quadrat at the obtained coordinates

• count and record the number of required plant species in the quadrat

• repeat steps 1-3, 9 more times to create 10 samples

• estimate the population size using the formula:

  population size = total area/area sampled x no. of species counted

required practical 9 - field investigation - part B - investigating distribution

• write a hypothesis on the effect of a change in light intensity on the distribution of a plant species

• lay down a tape measure from the base of a tree to an open area of ground

• place a quadrat along the 0 end of the tape measure, ensuring one corner is touching the 0 mark

• count the number of plants, and use a light meter (or phone app) to measure the light intensity and record results in a table

• place the quadrat 5m along the tape measure and repeat step 4

• repeat step 5 in 5m intervals until the end of the transect line is reached

• collate data from other investigators and find the mean no. of plants at each point along the transect

• plot a graph for distribution against light intensity, as the distance along the transect line increases

• compare results obtained with initial hypothesis

required practical - field investigation - risk assessment & sources of error

• wash hands thoroughly after experiment

• without repeating the experiment, the results from only one belt transect may be anomalous & unreliable