biology – form 3 page 46 ms. r. buttigieg unit 4 ... 4 2007.pdf · biology – form 3 page 46 ms....

Biology – Form 3 � Page 46 Ms. R. Buttigieg

Unit 4 Conditions supporting life

Predation: A predator is an animal that feeds by hunting and

killing its prey

The prey must escape from the

predator if it is to survive.

Competition: Individual plants and animals may have to compete

with each other for food, light,

water and space.

Disease: Some microbes cause diseases. A parasite is an

organisms that lives in or on

another organism called a host.

The parasite gets food from the

host causing it harm.

Grazers: These are animals that eat

plants. Also called

herbivores.

Biotic factors: Factors caused

by other living organisms

present in the community.

Human Activity: Industry, farming, forestry, transport and

housing have all affected the

survival of organisms by changing

their habitats.

Decomposers: Microbes that

break down dead and decaying

material and are important in

nutrient cycling.

Water: Needed for all life to survive. Organisms that live in dry

places (like camels and cacti) have

adaptations that cut down water loss.

In rivers and streams the animals and

plants have to withstand fast

currents. Seaweeds and seashore

animals have to cope with waves.

Temperature: Few living organisms can grow outside the range of 0 –

40oC.

But penguins can withstand

temperatures of –80oC in

the Antarctic.

Some bacteria have

adapted to live in hot

springs at over 100oC.

Abiotic factors: These can also be

referred to as Environmental

Factors or non-living factors.

Light: Needed for photosynthesis. Some plants are adapted to

live in the shade but others

live in full sunlight. On the

deep ocean beds or in deep

caves there is no light at all.

Air: Few organisms can live without oxygen (needed for respiration).

Animals use oxygen given by plants in

photosynthesis and give out carbon

dioxide. Carbon dioxide is used by

plants to give out oxygen.


Unit 4.1 Abiotic Factors

Two of the most important abiotic factors are: -

• Availability of water • Temperature

Availability of Water

How Water moves in plants:

Soil � cells of the root hairs � xylem � up the stem � leaves � evaporates out of stomata

4.1.1 TRANSPIRATION The loss of water from the plant’s leaves by evaporation is called transpiration.

Transpiration takes place through the stomata and a small amount through the waxy cuticle.

The flow of water up the xylem to the leaves is called transpiration stream. When water

evaporates from the leaves it creates a suction which pulls more water up the stem in the

xylem, thereby maintaining the flow of the transpiration stream. Root pressure also keeps

the upward flow of water since water continuously moves into the root forcing more water

upwards.

Answer the following:

1. Which tubes transport water up the plant

to the leaves?

2. Which tubes transport food up and down the leaf?

3. By which process does water enter the roots?

4. Where in the plant does evaporation occur?

5. What are the holes on the leaf underside called?

Xylem

vessel

Water

passes up

the stem in

xylem

Water and dissolved minerals enter

the root cells from the soil by

osmosis.

Root hairs provide a large surface

area for absorption.

Osmosis causes water to move from

cell to cell till it reaches the xylem

vessels.

The water moves up the stem to the

leaves in the transpiration stream.


FACTORS AFFECTING THE RATE OF TRANSPIRATION

1. The amount of light

2. Temperature

3. Air movement (wind)

4. Humidity

Transpiration is fastest when it is:

• Hot

• Dry

• Windy

It occurs mostly during the day as stomata are closed at night.

CONTROL OF TRANSPIRATION

Plants living in hot dry conditions (xerophytes) need to reduce the amount of water they lose

by transpiration. So they have special adaptations xeromorphic adaptations:

1. Closing of stomata: When the plant loses water, stomata become flaccid and

stomata close.

2. Position of stomata: Usually found on the lower surface of the leaves to

reduce water losses. The upper leaf surface comes in more direct contact

with the sun’s rays.

3. Number of stomata: Plants living in hot areas tend to have fewer stomata.

4. Sunken stomata: Many xerophytes have stomata found in pits. Water lost

accumulates in the pit above the stomata and creates a high humidity that

cannot be swept away by the wind, so preventing further evaporation.

5. Leaf fall: during the winter many trees shed their leaves to reduce water

loss, especially when the soil is frozen. Evergreen trees (do not shed their

leaves) have other ways of reducing water loss.

6. Leaf shape: Many xerophytes have leaves with a very small

surface area to reduce water loss. In fact the leaves of many

cacti are not broad but needle like.

7. Thick waxy cuticle: if it is shiny reflects sunlight and prevent loss of water.

Answer it: How have plants, which live in hot areas, adapted to reduce transpiration?

Biology – Form 3 � 9 Ms. R. Buttigieg

THE POTOMETER

Diagram and hand-written note:

Biology – Form 3 � 0 Ms. R. Buttigieg

4.1.2 THE IMPORTANCE OF OSMOREGULATION IN AMOEBA

Osmoregulation is another word for water balance. In protozoa such as Amoeba this function is carried out by the one or more contractile vacuoles that are generally present.

Mostly these are needed in freshwater organisms as marine

protozoa are found in a similarly concentrated solution so

little water flows into them.

Contractile vacuoles are generally located in the ectoplasm and act as pumps to remove excess water from the cytoplasm

so the Amoeba does not burst.

Water enters the amoeba’s body by osmosis and is removed by the rhythmic filling and

emptying of the contractile vacuole.

4.2.1 Temperature Variations and Plants Major temperature variations on Earth and their effect on the distribution of vegetation Temperature varies greatly from one region of the Earth to the other. However, there are 3

main variations that occur in 3 different regions namely:

1. Polar regions (Arctic and Antarctic)

2. Temperate regions

3. Tropical regions

1. Polar Regions – The Arctic and the Antarctic – referred to also as tundra

In these regions the temperature is below 00C for most of the year and the

ground is frozen. The tops of the mountains are also frozen. Not many organisms

can live in these conditions.

The plants growing in these areas are often small and grow close to the ground. Where soil

gathers in pockets or cracks in the rock, some small shrubs may also grow. Lichens and

mosses are also quite common in these areas. Small cushion plants that grow in a low, tight

clump and look like a little cushion are more common in these regions as their small size helps

them to survive the cold. They also have thick cuticles.

Contractile vacuole

Contractile vacuole Empties releasing water

Mitochondrion


Did you know there are two types of Rainforest -- the temperate

and the tropical? Tropical rainforests are found close to the equator. Temperate rainforests are found along coasts in the temperate zone, such as the Pacific Northwest of the USA. Both are endangered

2. Temperate Regions

The Temperate region has four seasons of winter, spring, summer, and fall. Animals and

plants have special adaptations to cope with these yearly changes. The trees are either

evergreen with tough needle like leaves or broad leaved deciduous trees.

The word "deciduous" refers to what the leaves on these trees do: change color in autumn,

fall off in the winter, and grow back again in the spring. This adaptation helps trees in the

forest survive winter.

Summer is a busy time for deciduous trees. Their broad leaves capture energy from the sun

and convert it to food by photosynthesis. Some of the food is used for growth and some is

stored in the roots for next spring. Temperatures vary between below 4oC in winter and

above 20oC in summer.

During the shorter days and cooler weather of autumn, green chlorophyll in the

leaves begins to decompose, revealing brilliant oranges, yellows, and reds.

To prepare for winter, deciduous trees and plants become dormant. They loose

their leaves and seal the places where leaves were attached with a protective

covering called a leaf scar. If they kept their leaves, the water in the leaves would freeze

into ice, damaging the leaves and leaving the plant vulnerable to bacteria or fungi. Plants also

make a concentrated sugar solution to stop water from freezing in their stems.

The longer days and warmer weather of spring signal to the trees to grow new leaves and

begin photosynthesis again.

Some plants die during the winter and leave underground storage organs or

resistant buds which give rise to new plants during the spring.

Found in Areas like

Britain, Western Europe,

Asia and North America

areas from the Great

Lakes region to the Gulf

of Mexico.


3. Tropic Regions

Tropical rain forests make up nearly half of all

forestland. In the tropics there are both wet and

dry seasons. Only those organisms that can survive

in hot, humid and wet conditions can live here.

Principally occur in Amazon Basin of south America,

Congo basin of central Africa and in or near

equatorial regions of southeast Asia and Indonesia.

Temperatures here range between 25oC and 32OC.

Humidity is seldom lower than 80%.

These include broad-leaved, mostly evergreen

plants in a hot, humid environment.

Rainforest plants have made many adaptations to their environment. With over 80 inches of rain per

year, plants have made adaptations that helps them

shed water off their leaves quickly so the branches

don't get weighed down and break.

� Many plants have drip tips and grooved leaves,

� Some leaves have oily coatings to shed water.

� To absorb as much sunlight as possible on the dark under store, leaves are very large.

� Some trees have leaf stalks that turn with the movement of the sun so they always

absorb the maximum amount of light.

� Leaves in the upper canopy are dark green, small and leathery to reduce water loss in

the strong sunlight.

� Some trees will grow large leaves at the lower canopy level and small leaves in the

upper canopy.

� Other plants grow in the upper canopy on larger trees to get sunlight. These are the

epiphytes such as orchids and bromeliads.

� Many trees have buttress and stilt roots for extra support in the shallow, wet soil of

the rainforests.

Look up the following: 1. Name 2 plants that live in each of the following habitats.

a. Polar regions b. Temperate regions c. Tropical regions

2. Name a country in the world in which one can find:

a. A Polar region b. a Temperate region c. a Tropical region

3. Name 2 adaptations that can be found in the vegetation occurring in each of the regions.

4. Name another region not mentioned here that is also a result of a different temperature.


4.2.2 Temperature control in humans

The Skin (see GCSE Biology pg. 137-139)

The skin has many important functions.

� It is the first line of defence against microbes and helps prevent injury to the body.

� It contains receptors that are sensitive to touch, pain, temperature and pressure that relay these messages to the brain.

� To make vitamin D

� To excrete waste

� It helps to keep you body temperature constant.

Keeping Body Temperature CKeeping Body Temperature CKeeping Body Temperature CKeeping Body Temperature Constant:onstant:onstant:onstant: Thermoregulation Thermoregulation Thermoregulation Thermoregulation is the process of keeping the

body at a constant temperature.

Human enzymes work best at 37°C (body temperature). The temperature of the body is monitored by a part of the brain called the hypothalamus. If you are too hot or too cold the hypothalamus sends nerve impulses to the skin, which has three ways to either increase or decrease heat loss from the body's surface.

1. Hairs on the skin trap more warmth if they are standing up, and less if they are lying flat. Tiny muscles in the skin can quickly pull the hairs upright to reduce heat loss, or lay them down flat to increase heat loss.

2. Glands under the skin secrete sweat onto the surface of the skin in order to increase heat loss by evaporation if the body is too hot. Sweat secretion stops when body temperature returns to normal.

3. Blood vessels supplying blood to the skin can swell or dilate (called vasodilation) - so that more heat is carried by the blood to the skin where it can be lost to the air; or shrink down again (called vasoconstriction) - to reduce heat loss through the skin once the body temperature has returned to normal


The skin is made up of mainly two layers:

• The epidermis • The dermis

The epidermis is divided into three layers:

1. The cornified layer - top most layer made up of dead cells. 2. The granular layer - made up of cells produced by the malpighian layer. 3. The malpighian layer - innermost layer which produces new cells. Cells contain melanin

which protect us against ultraviolet radiation.

The dermis is found beneath the epidermis and is made up of connective tissue. It has various structures including:

• Capillaries - supply skin with food and oxygen and help control body temperature through

vasodilation (hot temperatures) and vasoconstriction (cold temperatures). • Sweat glands - produces sweat which cools the body on evaporation. • Hair follicles - cornified cells that are formed into a tube. Hairs are raised by the hair erector

muscle when we are feeling cold. • Sebaceous glands - produce sebum that keeps the skin soft and supple and protects against

the entry of bacteria and pathogens into the body.

Modes of Action:


E

Revision questions

1. Is the hair made by the epidermis or the dermis?

2. Which structures in the skin of a furry mammal help to reduce water loss?

3. Sweating cools you down only if sweat can evaporate. a) In what conditions might the sweat be unable to evaporate from your skin? b) What conditions might speed up the evaporation of sweat and so make you feel very cold?


EENNDDOOTTHHEERRMM AANNDD EECCTTOOTTHHEERRMM AANNIIMMAALLSS

Endotherms are animals that can maintain a constant internal body temperature, regardless of the

temperature of their surroundings. Birds and mammals are endotherms. Humans have a constant

body temperature of 37 °C.

• Endothermy - This term refers to creatures that are able to control their body temperatures through internal means, such as muscle shivering, fat burning, and panting (Greek: endo = "within," therm = "heat").

• Homeothermy - A term used to define a creature that maintains a stable internal body temperature regardless of external influence. This temperature is often higher than the immediate environment (Greek: homoios = "same, identical," therm = "heat").

An ectotherm is an animal in which the internal body temperature is the same as the temperature of

its surroundings. Fish, amphibians, and reptiles are ectotherms. Ectotherms cannot control their

internal body temperature and therefore have to stay in either the sun to stay warm, or the shade to

keep cool.

• Ectothermy - This refers to creatures that control their body temperature through external means (Greek: ecto = "outside," therm = "heat"), such as the sun, or flowing air/water.

• Poikilothermy - This refers to creatures whose internal temperatures vary; often matching the ambient temperature of the immediate environment (Greek: poikilos = "varied," therm = "heat").

Examples of this temperature control include:

• Snakes and lizards sunning themselves on rocks. • Fish changing depths in the water column to find a suitable temperature. • Desert animals burrowing beneath the sand during the day.

HYPOTHERMIA – If body temperature falls below 35oC the hypothalamus stops working and the metabolic rate and body temperature cotninues to decrease resulting in coma and death


1: Read the following paragraph and then answer the set questions.

Mammals, including humans, and also the birds are often called endothermic (warm

blooded) animals. All mammals balance the heat produced in their bodies against the heat

lost through their skin. The main organ of temperature control is the skin. However, the

human being assists the natural mechanism by using clothes, heating, air-conditioning and

housing.

a) Describe the meaning of ‘endothermic (warm blooded) animals. (1)

b) Animals which are not endothermic (warm blooded) are said to be ectothermic

(cold blooded) animals. Describe the meaning of ectothermic (cold blooded) animals

and give 2 examples. (1,2)

c) Draw a large labelled diagram of the human skin. (5)

d) Describe how the human skin in adapted for temperature regulation. (6)

(15 marks)

JL 2000

2. The diagram below shows a section through the human skin.

a) Name the structures labelled A and B.

A _________________________________ B _________________________________

C _________________________________ D _________________________________ (4 marks)

b) Give one function of each of the following: (2 marks)

i. The Malphigian layer ________________________________________________________

ii. The fat layer ______________________________________________________________

C

D


4.3 Phototropism and Geotropism in Plants See GCSE Biology pg. 317 and 318 (including Experiment of Geotropism in Pea Radicles and Phototropism in Shoots) KNOW THE MEANING OF THE FOLLOWING: Tropism – Growth movements due to certain stimuli. Phototropism – Response to light. Geotropism – Response to gravity.

Work out Questions on Pg. 319 no. 1-4

How do the tropisms work?

Stems and roots produce growth regulating substances (hormones) at their tips called

auxins that:

• Stimulate the shoot to grow

• Cause the cells to elongate

Phototropism of Shoot

1. When a shoot only gets light from one

side most auxin is found on the shaded

side

2. The auxin makes the shoot grow more

on the shaded side

3. The shoot bends towards the light.

Geotropism in roots

1. In roots the auxin

builds up on the lower

side.

2. But this time, auxin

slows down growth in

the root.

3. So the upper side

grows quicker than

the lower side.

4. The root bends

downwards.

Geotropism in shoots

1. In the shoot, auxin builds up on the

lower side.

2. Auxin in shoots stimulates growth more

in the lower side.

3. This causes the shoot to bend upwards.

Auxin made by Shoot tip

LIGHT Shoot bends towards the light

LIGHT Auxin passes

sown the shaded

side

Auxin makes cells Elongate more on shaded side

Auxin made by root tip

Cells elongate more on upper side

Auxin builds up on the lower side

Auxin causes cells to elongate less in the lower side Root grows down

Shoot grows upwards


Biotic Factors

4.4. Competition for space, food and mates.

Competition See GCSE Biology pg.254

In a race all the competitors try their hardest to win. In nature, plants and animals compete for resources that are in short supply.

What do you think plants compete for?

If resources like light, space, water or nutrients are scarce, plants compete for them.

What do you think animals compete for?

Many animals compete for a territory (habitat). If they are not successful they do not attract a mate and can not breed.

Only those plants and animals that are able to compete successfully will survive. So competition restricts the size of a population.

There are 2 types of competition:

• competition between individuals of the same species • competition between individuals of different species. Competition within a species - Intraspecific competition

o Seedlings compete for space, light, water and nutrients. o Colonies of gulls compete for nesting sites.

Animals and plants tend to produce lots of offspring. Often there are far more than can ever survive. So there will be competition between individual offspring for scarce resources. Only the best adapted will survive to breed.

Competition between individuals of the same pecies means that only the 'best' genes are passed on to the next generation.

Competition between different species – Interspecific competition Have you ever seen a bird table in winter?

What happens when some crumbs are put on it?

Soon there are sparrows, starlings and other birds all trying to get at the food. The different garden birds are competing for a scarce resource - food.


Competing with humans

Can you think of any animals and plants that compete with humans? Weeds compete with the farmer's crops. There are many animals that compete with us - we call them pests. Locusts, cockroaches and rats are pests that compete with us for food. Greenfly and whitefly are pests that do damage to our crops. Competition exists both within the members the same species (intraspecific) and between different species

(interspecific competition)

4.5 Predator-prey relationships. (see GCSE Biology pg. 260)

Predators - Predators kill other animals (their prey) for food. Predators are usually bigger and fewer in number than their prey. They also have the following adaptations:

o Some hunt in a pack. They work together to catch the prey and share it.

o Attacking prey that is young, old, sick or injured. These prey are easier to overpower and kill. This also 'weeds out' the weaker individuals in the prey population.

o Catching large prey means that there is more food for the predator per kill.

o Not depending on one particular species of prey. If numbers go down. the predator can switch to another prey species.

o Migrating to areas where the prey is more plentiful.


Avoiding the predator – Adaptations of the prey that help them escape.

However well adapted the predator is, some prey escape. The following are some adaptations:

o Some try to run, swim or fly faster than the predator.

o Staying in large groups, like herds of antelope, helps survival. Many pairs of eyes can look out for predators.

o Some animals taste horrible! This makes them less attractive as a meal.

o Others like bees and wasps can sting the predator.

o Some prey has warning colours. This tells the predator to 'keep clear'.

o Some mimic poisonous animals, look like them but are not harmful so aren’t captured.

o Camouflage helps to hide the prey.

o Some prey try shock tactics to startle a would-be predator.

Prey that escape are usually the best adapted. They survive to pass on their genes to their offspring.

Predator-prey cycles The Italian mathematician Volterra is said to have developed his ideas about predation from

watching the rise and fall of Adriatic fishing fleets. When fishing was good, the number of

fishermen increased, drawn by the success of others. After a time, the fish declined, perhaps

due to over-harvest, and then the number of fishermen also declined. After some time, the

cycle repeated.

The idea that a system of predator and prey would cycle gained further support from analyses

of fur trapping records of the Hudson's Bay Company. The number of furs purchased at the

Company's forts was meticulously recorded, for well over 100 years. An analysis of the

numbers of snowshoe hares, and one of their main predators, the lynx, provides a remarkable

record of a predator-prey cycle. Peaks and valleys can be easily observed at roughly 8-10 year

intervals.


o The hare population increases to a level where the available winter food supply is largely exhausted.

o At that point, the hare population suffers an increase in death among young hares and a decrease in the birth rate.

o With fewer hares, the vegetation begins to recover from overbrowsing.

o Meanwhile, the lynx population increases as its main food supply, the hares, becomes abundant.

o When the hare population decreases, the lynxes swith to other prey; but, the alternate prey is not

adequate to support a large lynx population. o Now the lynxes experience increased mortality and a lowered birth rate. o Some lynxes leave the area entirely, searching for a place where food is more plentiful. o With fewer lynxes to watch out for and more vegetation to eat, the number of hares begins to

increase, and the cycle begins again. Work out the following:

1. Match the following words with the definitions. (ecosystems, population, habitat, niche, community,

biosphere)

a) organisms that interact within the same ecosystem: ____________________

b) a group of individuals of the same species: _____________________

c) the part of an ecosystem where plants and animals live: _____________________

d) all the ecosystems belong to this: _____________________

2. A population of rabbits lived on an island. Predators such as weasels fed on the rabbits. Some hunters came to the island and shot all the weasels. The rabbit population increased.

They began to compete for grass. Many rabbits starved. Soon the rabbit population was about the same as it was before the weasels were shot.

a) What were the 4 populations involved?

________________ ________________ ________________ ________________

b) Why do you think the hunters were wrong to shoot all the weasels?

___________________________________________________________________________

___________________________________________________________________________

c) What do you think will happen to the rabbit population in the future?

____________________________________________________________________________________

Note that: A population is a group of individuals of the same species living in a particular habitat.

e.g. a shoal of herring in the sea; dandelions in a lawn, owls in a wood.


4.6 Types of Nutrition & organism lifestyles

Different organisms obtain their food in different ways that can be grouped mainly into 2 types.

HETEROTROPHIC HOLOPHYTIC or AUTOTROPHIC Cannot produce their own food so take it Produce their own food. Build up all In a ready made form by digesting ready organic food substances e.g. sugar from made complex organic food material and simple substances e.g. water and CO2

absorb the products into their body. Carry out photosynthesis

1. Holozoic nutrition E.g. Green plants 2. Saprophytic nutrition Some Bacteria 3. Mutualistic relation (& nutrition) Some Protists e.g. Euglena 4. Parasitic nutrition

1. Holozoic nutrition – include organisms which take large food particles into their body. These are then digested (broken down) and the small soluble particles absorbed. E.g. humans

2. Saprophytic nutrition – feed on material by secreting enzymes on it. After being broken

by the enzymes, this food is then absorbed into the body of the organism. Food is egested outside their body. E.g. fungi and some bacteria

• Important as they decompose dead matter, releasing important substances back

into the soil, so keeping it fertile.

3. Mutualism – Involves 2 organisms living in a close association in which both benefit from each other. E.g. relation between herbivores and the bacteria living in their intestines; or the relation between bacteria and roots of leguminous plants (root-nodules)

see GCSE Biology pg. 296 4. Parasitic nutrition – Also involves a close association between 2 organisms, but in

this case one benefits and the other is harmed (the one being harmed is called the host).

• Examples of parasite include: o A flea living in the fur or feathers of mammals or birds

� Called an ectoparasite (as living outside host body) o A tapeworm, which feeds by taking food from the intestines of

man. � Called an endoparasite (as found inside the host)

Disease causing bacteria, fungi and protists are all parasites.

see GCSE Biology pg. 293


Biological Pest Control

There are 2 main ways in which a pest population can be reduced: 1. By using pesticides – chemical control. The problem with this method is that pesticides can damage the environment and they can kill other organisms as well. However it is very effective and kills pests quickly. 2. By using another organism to kill the pest – biological control. In this method, one finds a parasite or predator that attacks the organism that has become a pest. Biological control is better since it does not damage the environment. However it takes longer to decrease pests and it is sometimes difficult to find a good predator for your pest. Case Study of Biological Control in Australia Before 1859 there were no rabbits in Australia. But by accident some domestic rabbits escaped and they became wild. The population of these wild rabbits increased and they were damaging the people’s crops and gardens. The rabbits became pests. The people wanted to decrease the rabbit population. So they decided to introduce a virus, which attacked the rabbits and caused a disease known as myxomatosis. This virus killed down the rabbit population. However the virus also started attacking domestic rabbits. The virus itself had turned into a pest. So as can be noted from this example the introduction of alien (non-native) species can be dangerous. One must be sure that the predator only attacks the target organisms and that when the target organism is reduced it does not attack other beneficial organisms. Otherwise it would become a pest itself. Another example: In the 1930s a toad was introduced in Australia to reduce the cane beetle. However, the toad flourished and started eating anything. To make matters worse predators couldn’t control the toads since they were poisonous. Other examples of biological control are:

• Ladybird larvae to kill aphids (small insects that feed on plant leaves)

• In Malaysia barn owls are used to reduce rats in oil palm plantations

In Australia prickly pear cactus was reduced by the moth C. cactorum whose larvae feed on it.


4.7 HUMAN POPULATION GROWTH

See GCSE Biology Chapter 29 pg. 261-4 – Human Population The increase in population of the human species is a result of its control over most of the abiotic and biotic factors, which would have otherwise limited population size and spread.

Human populations can change too. At present the number of people on the planet is growing at an alarming rate. It has not always been so in the past. For thousands of years there was only a slow increase in the human population. Lack of food, diseases, wars and lack of shelter meant that people did not live very long.

Look at the graph: What do you think has caused the huge increases over the last 300 years?

Less developed countries: Less developed countries include all countries in Africa, Asia (excluding Japan), and Latin America and the Caribbean, and the regions of Melanesia, Micronesia, and Polynesia.

More developed countries: More developed countries include all countries in Europe, North America, Australia, New Zealand, and Japan.

o Improved agriculture means that most people are better fed. o Public health has improved. o There are better water supplies and sanitation. o Medical care has improved. o People can be vaccinated against many diseases. o Many disease-causing organisms can be controlled inside the body with drugs or

outside the body by other chemicals.


What has been the effect of all these advances?

o Fewer children are dying from disease and lack of food. o People are now living much longer.

o In Europe and North America the average life expectancy has risen to 68 years for men and 73 years for women. In India life expectancy has been much lower. But improved health and living conditions has now lifted the average life expectancy there to 56 years.

In 2000, the world had 6.1 billion human inhabitants. This number could rise to more than 9

billion in the next 50 years. For the last 50 years, world population multiplied more rapidly

than ever before, and more rapidly than it will ever grow in the future.

Anthropologists believe the human species dates back at least 3 million years. For most of

our history, these distant ancestors lived a risky existence as hunters and gatherers. This

way of life kept their total numbers small, probably less than 10 million. However, as

agriculture was introduced, communities evolved that could support more people.

World population expanded to about 300 million by A.D. 1 and continued to grow at a

moderate rate. But after the start of the Industrial Revolution in the 18th century, living

standards rose and widespread famines and epidemics diminished in some regions. Population

growth accelerated. The population climbed to about 760 million in 1750 and reached 1 billion

around 1800.

Work to do – Find some formation on the human world population and write it down on point form. Write 20 different points. Make sure they are linked together. You can add diagrams; charts and other material, which you think, may be suitable.

biology – form 3 page 46 ms. r. buttigieg unit 4 ... 4 2007.pdf · biology – form 3 page 46 ms....

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