The relationship between species, populations community and the ecosystem

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The relationship between species, populations
community and the ecosystem
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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). 
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Carrying capacity
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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.
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Carrying capacity of rabbits in a specific area
1. 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?
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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
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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

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Geometric growth form (J- curve)
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Logistic growth form (S-shaped curve)
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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

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Comparison between geometric (J-curve) and
Logistic (S-curve)
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Methods to determine population size1. Direct
method census
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A pitfall sampling method can also be used
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Methods to determine population size2. Indirect
method simple sampling
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Simple sampling can be used to determine the
number of plants in an area
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Quadrat sampling method for plants
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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
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Activity 1 simple sampling

• Method
• 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
• 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/jar
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Simple sampling can be used to determine the
number of micro organisms on a slide
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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
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Ave. number of worms in a plot
120100150130100
120 worms/plotEstimate number of
number of individuals in sample x habitat
sizeindividuals in the
__________________________population
sample size

Answer Simple sampling
24 000 worms
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Methods to determine population size2. Indirect
method mark recapture
A number of animals are caught and marked
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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.
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The same method are used with fish
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The fish are marked but dont take them out of
water for too long!
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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

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They are released back into the water and some
are caught again after a period of time
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The mark-recapture method can also be used on
frogs
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The mark-recapture method can also be used on
crabs
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Activity 2 Mark -recapture

• Method
• Get into groups of 4.
• 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.
• Mark 30 of your fish with a pen. Discuss how you
  should mark real fish.
• Put the marked fish back into your dam and mix
  them up with the rest of the fish.
• Take a handful of the mixed fish out of the dam.
  Count the marked and the unmarked fish.
• Estimate the size of your fish population by
  using the formula
• Repeat your estimate at least 5 times and
  calculate the estimated average fish in your dam.
  Tabulate your results.
• List possible shortcomings of your investigation

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              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
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Worldwide human population growth from 1750 to
2000
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Human population growth according to History
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Human population growth in SA from 1947 to 2011
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Human population age and gender distribution
in1. an increasing populationA 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 pyramid3. 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.
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Population sizes in different parts of the world
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The graph is divided into 2 groups1. 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
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Discuss the differences between the gender-age
pyramids for Japan Zimbabwe.
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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
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The effect of high population growth on the
environment
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The effect of high population growth on the
environment (depletion of resources and increased
pollution)
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The effect of a growing population on resources,
pollution, industrial output and the availability
of food
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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.
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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.
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• 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.

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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
earths capacity to regenerate
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In 2006, the global ecological footprint outpaced
the Earths 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
Earths 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.
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What are we doing?
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Activity 3Use 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




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The effect of high population growth on the
environment. The darker the colour, the greater
the ecological footprints.
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Reckless consumption is depleting the worlds
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 Earths 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 worlds
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 worlds people live in
nations that are ecological debtorstheir
national consumption has outstripped their
countrys 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.
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The following categories affect your ecological
footprint
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Ecological footprint" for different countries
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(No Transcript)
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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.
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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.

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What can you do to save the world?
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Sustainable careful use of natural and human
resources so that they will also be available
to future generationsConservation the
management of the Earths resources so that it
yields the greatest sustainable benefit to
future generations while maintaining its
potential to meet the needs of future
generations
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Human demands versus conservation in the
harvesting of natural resourcesAbalone poaching
is illegal
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Human demands versus conservation in the
harvesting of natural resources Oysters need to
be a specific size before it may be harvested
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Human demands versus conservation in the
harvesting of natural resources During 2010 more
than 300 rhinos 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 rhinos were killed in SA since 2000
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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.

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Herds of wildebeest
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School of fish
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Some Predators form packs as an efficient hunting
strategy like wild dogs
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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.
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They chase until their prey tires, reaching
speeds up to 55 kmph, and sometimes
disembowelling prey while it is still running
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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.
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Sharks also hunt in groups
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Group hunting improves efficiency. By hunting in
groups a predator can kill larger animals than a
single animal can kill
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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.

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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

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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.

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Dominant breeding pairs - meerkat

• Meerkats 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.

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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 dont 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.
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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 colony
• Honey 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

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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
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Identify the different members of a bee colony
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The workers (females) collect pollen and nectar
every day
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Some pollen collect in a packet around their legs
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Nectar and pollen is stored as honey
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Honey is stored to feed the developing embryos
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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
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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.
85
Workers have a special wagging dance with which
they communicate with other workers on the
distance and direction of food sources
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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.

87
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!