the relationship between species, populations community and the ecosystem

The relationship between species, populations community and the ecosystem

Developed by KZN advisors

Carrying capacity is the maximum population size a certain environment can support for an extended period of time, for a population of a particular species.

Under ideal conditions, a population naturally increases until it overshoots the carrying capacity. At this point, the environment can no longer provide for the species, due to a number of different environmental resistances, including food, crowding, competition, etc. The population, due to lack of resources, will begin to die out, allowing the environment to recover. As the environment recovers, the species population is able to flourish once more. This leads to a fluctuation between the prosperity of the species and the prosperity of the environment (hence the fluctuations in the graph).


Carrying capacity


If a population reaches carrying capacity it can remain stable or move

up and down (fluctuate). If there is

more rainfall and more food available the carrying capacity increases and the

population will increase until it reaches the new carrying capacity before

it levels off again. If there is habitat

destruction or a draught the carrying capacity

decreases and the population will decrease until it reaches the new

carrying capacity and levels off again. Developed by KZN advisors

Carrying capacity of rabbits in a specific area1. What does the blue line represent? What does the purple line represent? What does it mean when the purple line rises above the blue line? 2. Which of the following situations might cause the purple line to decrease below the blue line: abundant food sources, lack of competition, a young population, or plentiful roaming space?

3. Can you think of any events that would cause the purple line to stay above the blue line indefinitely?


1.1 Suggest THREE reasons why the growth form between the period 1920 and 1935 is as it is.1.2 What is the growth phase called between 1910 and 1920? (1)1.3 During which year did the jackal enter the fenced area? Give a reason for your answer from

the information supplied. (3)1.4 Between 1940 and 1950 the springbok population increased again. Mention a possible reason

for this increase. (2)1.5 Mention FOUR other factors, besides the jackals, which could have caused the decline in the

springbok population between 1935 and 1940? (4)1.6 What method was most probably used to determine the size of the springbok population? (1)1.7 Do you think the line representing the carrying capacity is accurate?

Give a reason for your answer. (3)1.8 The population between 1965 and 1975 appears to have stabilised. Suggest how the farmer

might be controlling the population. (2)1.9 What do you notice about the growth from 1915 – 1925 and 1940 – 1950? (1)

(20)

Question: Carrying capacity


Density dependent and factors

Density dependent Density independent

a density-dependent factor affects a greater percentage of individuals in a population as the number of individuals increases; it will also affect each individual more strongly. Population growth declines because death rate increases, birth rate decreases or both. Resource limitation is one such density dependent factor. A reduction in available food often limits reproductive output as each individual produces fewer eggs or seeds. Health and survivorship also decrease as crowding results in smaller, less robust individuals. Many predators concentrate on a particular prey when its population density is high, taking a greater percentage than usual.

Density-independent factors affect the same percentage of individuals regardless of population size. Weather, climate and natural disasters such as freezes, seasonal changes, hurricanes and fires are examples; the severity and time of occurrence being the determining factor on what number of organisms is affected. In some natural populations, these effects routinely control population size before density-dependent factors become important


Geometric growth form (J- curve)


Logistic growth form (S-shaped curve)


Question : growth patterns• 4. A certain fast growing unicellular micro-organism is cultivated in a sugar solution in a closed test tube at

250 C. At regular intervals, samples were taken in order to calculate the population size. The graph below was drawn from the data obtained. Study the graph and answer the questions that follow.

• • • • • • •

• 4.1 Which specific organism was most probably cultivated in the test tube? (1)

• 4.2 Name the growth phases indicated by A, B and C respectively. (3)• 4.3 Give an explanation for the specific growth pattern of each of the phases A, B and C. (6) 4.4 What is phase Y called and what is the possible cause, thereof, for this specific population in particular?

(3)• [ 13 ]


Comparison between geometric (J-curve) and Logistic (S-curve)


Methods to determine population size1. Direct method: census


A pitfall sampling method can also be used


Methods to determine population size2. Indirect method: simple sampling


Simple sampling can

be used to determine the

number of plants in an

area


Quadrat sampling method for plants


In simple sampling a physical count of all the animals/plants under investigation in a small sample are of the habitat is done. The total population in the big area is calculated as follows: Estimate number of = number of individuals in sample x habitat sizeindividuals in the __________________________population sample size


Activity 1: simple samplingMethod

Mix an unknown number of tiny beads with sea sand thoroughly to fill a 500 ml jar.

Remove a level teaspoon (5 ml) of the mixture from the jar.

Spread the mixture on a saucer and count the number of beads.

Use the formula below to estimate the total number of beads in the bottle :

Total nr. of beads = nr. of beads in sample x total volume of mixture (500 ml)

____________________________

volume of teaspoon (5ml)

Place the bead and sea sand mixture back into the jar.

Mix thoroughly and repeat the exercise a few more times.

Obtain an average estimate of the number of beads in the jar

Results

Complete the table :-

Questions

1.Why is it necessary to repeat the

investigation a number of times?

2. How is this investigation limited?

Investigation Total population

1

2

3

4

5

Ave estimate of beads/jarDeveloped by KZN advisors

Simple sampling can be used to determine the number of micro organisms on a slide


A leading Kwa-Zulu entomologist ( a person that studies insects ) decided to work out the number of worms that occurred in Kwa-Mashu. The total area in Kwa Mashu where the worms occurred was 2000 m2. He chose five 10 m2 plots and found 120, 100, 150, 130 and 100 worms in each plot respectively. (i) Estimate the total number of worms in the Kwa-Mashu area. (Show ALL calculations). (5) (ii) Describe two ways how the entomologist could improve the reliability of these results. (2)

(7)

Question : Simple sampling


Ave. number of worms in a plot = 120+100+150+130+100 =

= 120 worms/plot

Estimate number of = number of individuals in sample x habitat sizeindividuals in the __________________________population sample size

=

plots5

600

m

mx

10

2000120

= 24 000 worms

Answer : Simple sampling


Methods to determine population size2. Indirect method: mark recapture

A number of animals are caught and marked


In theory, mark / recapture techniques involve sampling a population of animals and then marking all of the individuals captured in a recognizable way. The

marked animals are then released back into the population and left to mingle for a suitable period of time. Once they have become thoroughly mixed into the population again, the population is re-sampled.The assumption is then made that the proportion of marked animals in the second sample is the same as

the proportion of marked animals to non-marked within the whole population. Enough time must be

allowed to elapse for complete mixing to have occurred.


The same method are used with fish


The fish are marked – but don’t take them out of water for too long!


The following should be taken into account when animals are caught and marked

1. The animal usually needs to be captured to be marked, the animal should not be injured and its behaviour pattern should not be altered.

2. The mark used should not harm the animal - for example a dot of a particular paint may turn out to be toxic to the animal. Trials therefore need to be done to ensure that the animal is not harmed in any way.

3. Take random samples from the population. If you take samples from only one place each time, they you are likely to catch the same animals that you released.

4. Once you have released the first sample, give the animals enough time to mix randomly with the rest of the population before you take the second sample.

5. Ensure that animals do not become 'trap-shy' and avoid the traps after the first capture. This can be reduced as far as possible by choosing a method which will not distress the animal unduly. Some animals may become 'trap-happy', particularly if the traps are baited. This can be overcome by setting out the baited traps, without actually trapping, for some time before the first sample is taken. This allows all animals in the population to become equally trap-happy before you start.

Trap-shyness results in population overestimates, while trap-happiness results in population underestimation


They are released back into the water and some are caught again after a period of time


The mark-recapture method can also be used on frogs


The mark-recapture method can also be used on crabs


Activity 2: Mark -recaptureMethod:

1.Get into groups of 4.

2.Tear old papers (newspaper/unused notes) into small pieces and throw into a container. The container will represent a dam and the paper pieces fish. You should have ± 100 - 200 fish in your dam.

3.Mark 30 of your fish with a pen. Discuss how you should mark real fish.

4.Put the marked fish back into your dam and mix them up with the rest of the fish.

5.Take a handful of the mixed fish out of the dam. Count the marked and the unmarked fish.

6.Estimate the size of your fish population by using the formula:

7.Repeat your estimate at least 5 times and calculate the estimated average fish in your dam. Tabulate your results.

8.List possible shortcomings of your investigation

sampleondtheinsindividualmarkedofnumber

sampleondtheinnumberxsamplefirsttheinnumbersizePopulation

sec

sec


It is evident from the graph that :-1. the human population is increasing rapidly and shows a geometric (J-shaped) growth form2. the population is doubling in shorter periods3. the next doubling period (8 000 million) has been calculated to be in the year 2010 – a doubling period of 35 years4. this increase in population CANNOT go on indefinitely – as environmental resistance (shortage of food, O2 and living space) increases – something has to give – unless we are able to stabilise the population at the carrying capacity of the world

Trend in the human population growth up to 1650 and from 1650 to the present moment


Worldwide human

population growth

from 1750 to 2000


Human population growth according to History


Human population growth in SA from 1947 to 2011


Human population age and gender distribution in:

1. an increasing population

A population pyramid with a small number of old people indicates a population with a high birth rate, a high death rate and a short life expectancy. This pattern is typical of less economically developed countries (LDC) like South

Africa, South America and Asia (excluding Japan)

2. a stable populationThere is approximately the same number of young people

and old people. About the same number of children is born each year compared to the number of people who die each year. Economical developed countries like Ireland have this

kind of pyramid

3. a decreasing populationThere are more old people than young people. Each year more people die than are born. Developed countries like

Germany have this kind of pyramid. Some southern African countries, like Botswana (experiencing the effects of

HIV/AIDS) are also starting to show this kind of age-gender pyramid.


Population sizes in different parts of the world


The graph is divided into 2 groups:1. The less developed countries (LDC) like Latin America, Africa and Asia (excluding Japan). Population growth is expanding rapidly and the majority of people live in poverty. Medical care and technological advances are not readily available, food is scarce and levels of education are low. A high social value is placed on large families.2. The more developed countries (MDC) like North America, Australia and Europe. Population growth is low and people enjoy a good standard of living. Medical care and technology is readily available. Food and technology are available, level of education is high.

A comparison of less developed countries with more developed countries


Discuss the differences between the gender-age pyramids for Japan & Zimbabwe.


Use these graphs to discuss the changing trends in the SA population. Indicate the working group (20 – 60 years), mention how their economical contributions will support the non-economical groups (children and old people). Take the % of jobless people into consideration and the fact that only 5.6% of the population pays tax


The effect of high population growth on the environment


The effect of high population growth on the environment (depletion of resources and increased pollution)


The effect of a growing population on resources, pollution, industrial output and the availability of food


Ecological footprint: the impact of a person, city, or country on the ecology of a local area or the whole planet. It is a measure of how much land and water a person, city or country needs and the wastes that are produced.


We do not know what the carrying capacity of the world is. The United Nations has predicted a

global human population of over 10 billion people by 2050 – therefore an estimated 4

billion people will be added to the population in the next 40 years.

One approach to estimate the carrying capacity of the earth is to look at the ecological footprint

of different groups of humans.


• According to the Global Footprint Network, humanity uses the equivalent of 1.3 planets to provide the amount of resources we consume and absorb the waste we produce. This means it now takes the Earth one year and four months to regenerate what we deplete in a year.


To calculate the ecological footprint of a population all their needs need to be taken into account, e.g. food, water, fuel, building materials, clothing and

medical care. The impact, to produce the needs, on the environment is then calculated. An ecological footprint represents the area of land and water

utilised by a particular nation. It takes into account the resources used by wastes produced by that country. It measures how much land an water a human population requires to produce what it

consumes, and to absorb its wastes using current technology. It compares human demand with the

earth’s capacity to regenerate Developed by KZN advisors

In 2006, the global ecological footprint outpaced the Earth’s biological capacity by 30 percent. This trend is increasing. In fact, on September 23rd of this year, we passed “Overshoot Day,” the day the human ecological footprint exceeded the Earth’s biocapacity and began living beyond its ecological means. Since then, we have been engaged in the ecological equivalent of deficit spending: our rate of resource consumption is exceeding the rate at which those resources can be naturally replenished.


http://www.footprintnetwork.org/en/index.php/GFN/page/glossary/#overshoot

What are we doing?


Activity 3:Use the next two slide to complete the table:

Greater ecological footprint than South Africa

Similar ecological footprint to South Africa

Smaller ecological footprint than South Africa

Australia Ethiopia India


The effect of high population growth on the environment. The darker the colour, the greater the ecological footprints.


Reckless consumption is depleting the world’s natural capital to a point where we are endangering our future prosperity. The Living Planet Index shows that over the past 35 years along the Earth’s wildlife populations have declined by a third. Yet our demands to continue to escalate, driven by the relentless growth in human population and in individual consumption. Our global footprint now exceeds the world’s capacity to regenerate by about 30%. If our demands on the planet continue at the same rate, by the mid-2030s we will need the equivalent of two planets to maintain our lifestyles. The ecological credit crunch is a global challenge. The Living Planet Report 2008 tells us that more than three quarters of the world’s people live in nations that are ecological debtors—their national consumption has outstripped their country’s biocapacity. Thus, most of us are propping up our current lifestyles, and our economic growth, by drawing (and increasingly overdrawing) upon the ecological capital of other parts of the world.


The following categories affect your ecological footprint:


Ecological “footprint" for different countries


It is likely that the countries and regions with surplus ecological reserves, and not the ones relying on continued ecological deficit spending, will emerge as the robust and sustainable economies and societies of the future.


What will happen if this trend continue?•If everyone lived like me, we'd need 3.5 planets to provide enough resources. •To support my lifestyle, it takes 15.4 acres of the Earth's productive area. •If everyone lived like me, we'd need 3.5 planets to provide enough resources. •To support my lifestyle, it takes 15.4 acres of the Earth's productive area.


What can you do to save the world?


Sustainable: careful use of natural and human resources so that they will also be available to future generationsConservation: the management of the Earth’s resources so that it yields the greatest sustainable benefit to future generations while maintaining its potential to meet the needs of future generations


Human demands versus conservation in the harvesting of natural resources

Abalone poaching is illegal



Oysters need to be a specific size before it may be harvested



During 2010 more than 300 rhino’s have been pouched and killed for their horns in South Africa. The sad truth is that a rhino is worth more dead than alive. A rhino horn is valued at $20 000 (R140 000) per kg

and a rhino horn weigh up to 5 kg. Currently a live rhino is sold at R130 000 – R300 000.

678 rhino’s were killed in SA since 2000


Social organisation enhance survival of species

Animals that live in herds, schools, swarms, and flocks typically give up on their individual defences because they pursue another survival strategy. If you are a member of a herd, you do not need to run faster than your predator; you only need to run faster than the slowest member of

your herd. The individual defence IS forming the herd where the weak are daily sacrificed to earn the others

one more day of untroubled life, until it is their turn. It is creepy to watch video footage of lion hunting the

antelopes: after a brief chase, the herd is standing still and staring at their member being eaten alive, chewing

their cud. That's what herd is about.Developed by KZN advisors

Herds of wildebeest


School of fish


Some Predators form packs as an efficient hunting strategy like wild

dogs


African wild dogs form packs of up to 40 members, each with a dominant breeding pair that remain monogamous for life. These gregarious animals are co-operative hunters, relying on sight rather than smell to pinpoint their prey. Hunts tend to occur at dawn and dusk, but on occasion the dogs will venture out if there is a full moon.


They chase until their prey tires, reaching speeds up to 55 kmph, and sometimes disembowelling prey while it is still running


African wild dogs live in packs of 6 to 20. The aggression exhibited towards prey is completely nonexistent between members of the pack and there is little intimidation among the social hierarchy. Their large range of vocalizations includes a short bark of alarm, a rallying howl and a bell-like contact call that can be heard over long distances. Elaborate greeting rituals are accompanied by twittering and whining. The entire pack is involved in the welfare of the pups, which are born in thick brush or in a den.


Sharks also hunt in groups


Group hunting improves efficiency. By hunting in groups a predator can kill larger animals than

a single animal can kill


Animals with dominant breeding pairs- the giant otter

Giant otters live in groups with one breeding pair. There is one dominant female in the group She has many offspring and is also the top fish catcher and the leader of the hunt.


Animals with dominant breeding pairs – Lions

The advantages of dominant breeding pairs are:- offspring are cared for by many members of the group- dominant males and females are usually the strongest and most efficient members of the group, their genetic material will be carried to the next generation


The Southern ground hornbill

The Southern ground-hornbill occurs from Kenya to southern Africa, living in a wide range of grassland, savannah woodland habitats. In South Africa, it is listed as Vulnerable, with an estimated population of just 1500-2000. It eats a wide range of food, especially animals, such as grasshoppers, frogs, mongooses and bird nestlings. It is a monogamous, cooperative breeder, with a group consisting of a dominant breeding pair and 0-9 helpers, who are usually either adult males, or juveniles from previous breeding seasons. It lays 1-2 eggs, which hatch in the sequence laid, meaning that the one chick is 3-14 days older than the other chick. The younger chick is unable to compete for food with its older sibling, and dies of starvation when it is rarely 3-4 weeks old. Current conservation measures include hand-rearing of the otherwise redundant second born chicks, captive breeding and reintroduction.


Dominant breeding pairs - meerkatMeerkats are facultative monogamous, which means that they breed with only one other member of the opposite sex. The female does not depend on the male for help raising the pups. She depends instead on kin and non-kin helpers. Cooperation in meerkat breeding is obligate because the breeding female cannot reproduce and raise offspring without help. Subordinate meerkats occasionally breed, but the dominant pair is always responsible for the majority of reproduction.


The alpha pair mates for life, though life span is limited by predation. Turnover in the dominant male position is higher than in females because males are more likely to leave the territory, and meerkats off of their territory are likely to be preyed upon. The mating pair shares little or no relatedness

Availability of resources limits meerkat breeding. Rainfall triggers breeding because rain increases plant life which in turn increases the population of arthropods that serve as meerkats’ prey. In fact, reproductive success for a band as a whole depends directly on the amount of rain during the rainy season

Because rainfall is unpredictable, breeding meerkats must have a mate at all times so that they don’t miss any breeding opportunities. If they had to spend part of the rainy period wooing a mate, they would run the risk of breeding too late into the season. The rain and the corresponding increase in arthropod abundance would end before the critical period of offspring growth, or even before the birth of the offspring. Reproduction also depends on the presence of helpers. Meerkats are monogamous because there are only enough helpers for one litter. With only one litter, there can be only one breeding female, and competition for the position results. The breeding female has her choice of males, and she chooses the one with the best genes. He proves himself to her by competing for and attaining the alpha male position.


Bees live in a colony with division of labour

There is one queen to each colony, and she is much larger in size than the other bees. Her main task is to lay eggs. Reproduction can take place only by means of the queen, and no other females are able to mate with the drone males. In addition to laying eggs, the queen also secretes important communicative substances that maintain the unity of the colonyHoney bee eggs hatch regardless of whether they are fertilized. Drones develop only from unfertilized eggs. Unfertilized eggs are haploid in origin, which means that they contain only 16 chromosomes from their mother. Honey bees are a haplo-diploid species, in which drones have haploid cells and workers and queens have diploid cells


http://www.statemaster.com/encyclopedia/Haploid

http://www.statemaster.com/encyclopedia/Chromosome

http://www.statemaster.com/encyclopedia/Ploidy#haplodiploidy

The drones are larger than the female workers, though they lack stings and the necessary organs to collect food for themselves. Their only function is to fertilize the queen.

The worker bees perform all such other tasks that you might imagine, including making the waxen combs in the hive, gathering food, producing royal jelly, regulating the temperature in the hive, cleaning it of debris and defending it


Identify the different members of a bee colony:


The workers (females) collect pollen and nectar every day


Some pollen collect in a packet around their legs


Nectar and pollen is stored as honey


Honey is stored to feed the developing embryos


Developing larvae: responsibility for caring for the larvae falls to the worker bees in the hive, which prepare incubation cells in a region specially set aside in the combs where the queen can lay her

eggs


Worker bees feed the newly-hatched larvae with great care and selflessness. In fact, it has been established that worker bees will visit any single larva some 10,000 times

during its period of growth. For the first three days after they hatch, the larvae are fed on royal jelly. During this larval stage, the young bees are fed constantly and undergo

their greatest physical development. As a result of their regular feeding during this phase, the larvae's weight increases by up to 1,500 times in only six days.


Workers have a special wagging dance with which they communicate with other workers on the distance and direction

of food sources


Division of labour among members of a colony, e.g. an ant colony

Sociality is more advanced in bees, ants, and termites. As a rule, only one female (a queen) lays eggs in a colony, and numerous workers are sterile. Workers are involved in other functions like construction, defence and taking care of juveniles. They often have a division of labour and corresponding morphological differences.


Termites with different members and division of labour

This picture shows some forms (casts) of termites. Social insects have very complicated behaviour. Their success largely depends on coordinated actions of many individuals. For example, leaf-cutting ants have underground fungus gardens. Ants bring foliage to this garden and collect fungus for food. This is insect agriculture!


the relationship between species, populations community and the ecosystem

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