19 Populations In Ecosystems

Question 1

What is a population

Answer 1

A group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed

Question 2

What is a community

Answer 2

all the populations of different species living and interacting in a particular place at the same time

Question 3

What is a habitat

Answer 3

Place where an organism normally lives and is characterised by physical conditions and the other types of organisms present Within each habits there are smaller units each with their own microclimate, these are called microhabitats

Question 4

What is an ecological niche

Answer 4

Describe how an organism fits into an environment, refers to where an organism lives and what it does there, Includes all biotic and abiotic conditions to which an organism is adapted in order to survive reproduce and maintain a viable population

Question 5

Why can no population continue to grow in definitely

Answer 5

Certain factors limit growth for example the availability of food light water oxygen and shelter and the accumulation of toxic waste, disease, and predators Each population has a certain size, the carrying capacity, that can be sustained over a relatively long period and this is determined by these limiting factors

Question 6

What happens To warm blooded animals in extreme temperatures

Answer 6

More energy to maintain body temperature Leaves less energy for growth and so they mature more slowly and reproductive rate slows, carrying capacity of population is therefore reduced

Question 7

What is the competitive Exclusion principle

Answer 7

No two species can occupy the same niche indefinitely when resources are limiting When populations of two species are in competition one will have a competitive advantage over the other normally One population will increase in size while the other will diminish If conditions remain the same this will lead to the complete removal of one species

Question 8

Type of into specific relationship

Answer 8

Predator prey relationships A predator is an organism that feeds on another organism known as their prey

Question 9

How have predators and prey evolved

Answer 9

Predators, Faster movement more affective camouflage better means of detecting prey Prey, Better camouflage more protective features such as spines concealments behaviour

Question 10

Relationship between predators and the prey and its affect on population size

Answer 10

Predators eat their prey reducing population of prey With fewer prey available predators are in greater competition with each other for prey that are left Predator population is reduced as some individuals unable to obtain enough prey for survival or to reproduce With fewer predators left fewer prey are eaten and so more survive and are able to reproduce Prey population therefore increases With more prey now available as food, predator population increases

Question 11

In natural ecosystems fluctuations of predator and prey population sizes are less severe why is this the case

Answer 11

Organisms eat a range of foods and therefore the fluctuations are less severe

Question 12

What other than predator prey relationships causes fluctuations in populations

Answer 12

Disease and climactic factors also play a part , these periodic population crashes are important in evolution as there is a selection pressure which means that those individuals who are able to escape predators are more likely to survive and reproduce

Question 13

What is abundance

Answer 13

Number of individuals of the species in a given space

Question 14

Which sampling techniques used in study of habitats

Answer 14

Random sampling using Frame quadrat or point quadratic Systematic sampling along a belt transect

Question 15

What is a point quadrat

Answer 15

Horizontal bar supported by two legs, at set intervals along horizontal bar 10 holes through which a pin may be dropped, each species that touches the pin is then recorded SEE TXTBOOK PG 481

Question 16

What is a frame quadrat

Answer 16

Square frame divided by string or wire into equally size subdivisions, abundance of each species within quadrat is recorded SEE TXTBOOK PG 481

Question 17

Three factors to consider when using quadrat

Answer 17

Size of quadrat, depends on size of plants or animals being counted and how they are distributed within the area, Where a population of species not evenly distributed large number of small quadrats will give more representative results Number of sample quadrants to record within the study area Position of each quadrat within the study area, random sampling must be used to avoid bias

Question 18

Method of random sampling when using quadrat

Answer 18

Lay out 2 long tape measures at right angles along two sides of study area Obtain a series of coordinates by using random numbers taken from a table or generated by computer Place a quadrat at the intersection of each pair of coordinates and record the species within it

Question 19

What is a belt transect and what is its importance

Answer 19

Made by stretching a string or tape across the ground in a straight line, a frame quadrat is laid down alongside the line in the species within it is recorded, process is repeated Important with some form of gradual change (transition) in communities of plants and animals take place, for example distribution of organisms along a line of succession

Question 20

For species that don’t move around abundance can be measured by taking into account either

Answer 20

Frequency, likelihood of particular species occurring in a quadrat Percentage cover, an estimate of the area within a quadrat that a particular plant species covers

Question 21

To obtain reliable results When using quadrat it is necessary to ensure that

Answer 21

Sample size is large, so many quadrats used and mean of all samples is obtained

Question 22

Mark release recapture technique

Answer 22

Known number of animals are caught, marked in some way and then released back into community Sometime later a given number of individuals are collected randomly a number of marked individuals are recorded Estimated population size = total number Of individuals in the first sample x total number of individuals in the second sample/ number of marks individuals recaptured

Question 23

Assumptions of Mark release recapture technique

Answer 23

Proportion of marked to unmarked individuals in second sample is same as population as a whole Marked individuals released from the sample distribute themselves evenly amongst remainder of population and have sufficient time to do so Population has a definite Boundry so no immigration into emigration out of population There are a few if any deaths and births within the population Method of marking is not toxic to individual nor does it make individual more conspicuous and therefore more liable to predation Mark or label is not lost or rubbed off during investigation

Question 24

What is succession

Answer 24

Term used to describe changes of ecosystem as populations fluctuate over time in the species that occupy a particular area

Question 25

New species may colonise an area and change environment they may alter environment in a way that makes it

Answer 25

Less suitable for the existing species as a result the new species may outcompete the existing one and so take over given area More suitable for other species with different adaptations as a result the species may be out completed by the better adapted new species In this way series of successional changes alter the abiotic environment Alterations can result in less hostile environment that makes it easier for other species to survive, New communities are formed and biodiversity may be changed

Question 26

First stage of succession is

Answer 26

Colonisation of an inhospitable environments by organisms called pioneer species

Question 27

Pioneer species make up a pioneer community and have features that suit them to colonisation these include

Answer 27

Asexual reproduction so that a single organism can rapidly multiply Production of vast quantities of wind dispersed seeds or spores, easily reach isolated situations Rapid germination of seeds on arrival as they do not require a period of dormancy Ability to photosynthesise as light is available but other food is not so don’t depend on animal species Ability to fix nitrogen from atmosphere because soil may have few nutrients Tolerance to extreme conditions

Question 28

What is the climax community

Answer 28

Species may flourish and much biodiversity Due to stable state comprising balanced equilibrium of species

Question 29

Features that emerge during any succession

Answer 29

Abiotic environment becomes less hostile Great number and variety of habitats and niches Increased biodiversity as different species occupy these habitats More complex food webs Increased biomass

Question 30

Another type of succession is

Answer 30

Secondary succession, occurs when land that has already sustained life is suddenly altered Process by which ecosystem returns to climax community is same but normally occurs more rapidly

Question 31

What is conservation

Answer 31

Management earths natural resources by humans In such a way that maximum use of them Can be made in the future Involves active intervention by humans to maintain ecosystems and biodiversity

Question 32

Main reasons for conservation

Answer 32

Personal, ethical (other species have occupied earth far longer and should be allowed to coexist) economic (long-term productivity is greater if ecosystems are maintained in natural balanced state) and cultural and aesthetic

Question 33

Why are many species that existed in early stages No longer present as part of the climax community

Answer 33

Their habitats have disappeared as a result of succession or species have been outcompeted by other species or they have been taken over by human activity One way of considering these habitats and hence the species they contain is by managing succession in a way that prevents a change to the next stage