BALANCE OF NATURE.
Nature comprises of physical components of the universe which together
form natural environment
The natural environment is an area in which living and non- living
things are found. This could be land, water, air, microorganisms,, clouds,
animal, plants.
In the natural- environment
living things form abiotic component for
the life of organism to continue there
must be a certain proportion of each type of organism that will safely interact
with each other and with the natural environment.
When the proportion is maintained nature is said to be balanced.
Importance of the natural environment
Importance of the natural environment
The natural environment is importance because
•
It is
the source of food for organism
•
It provide shelter and security for organisms
•
It
provides an appropriate setting for organisms to produce and increase in number
•
It
allows living and non- living things to interact
The terms which are important when studying
the natural environment
Biotic factors- Are all the living components of the environment. They
include plants, animals and microorganism.
Abiotic factors- are the non-living components of the environment, for
example light, water, rocks and soil.
Ecology- Is the branch of biology that deals with the study of the
relationship between living things and their natural environment.
Population- is the total number of a certain species of organisms in a
community, for example the number of frogs in a pond.
Community- refers to the populations of different organism living in a
specific area called a habit eg. A grassland community could include grass
acacia trees, lions, antelopes, giraffes and cheetah .
Habitat- is a specific area with a specific set of conditions that is
appropriate for a certain community and where that community lives.
Eg. Tropical rainforest, a desert, a swamp, a pond, a grass land and
an ocean.
Ecosyotem- Refers to a natural unit made up of living and non- living
things whose interaction leads to a set-sustaining system.or
s a natural unit composed of living and non living components that interact and exchange materials with each other, e.g. pond, forest, seashore.
Biosphere (Ecosphere) Is the part of planet earth
inhabited by living organisms, this included water, land and air.
Biome is a large area of earth surface with particular
climatic factor hence similar life form and environmental conditions, e.g. Savannah
Populations; a group of organisms of the
same species in a given space and time, e.g.; elephants in Momela National Park
Ecological niche; Is the exact place an
organism occupies and its role in the habitat, i.e.; the role of species in the
food web/chains.
Carrying capacity; Total number of members of
a given species that an ecosystems can support without depleting the various
resources.
Environment; surroundings (biotic and
abiotic) where living organisms live. The presence of plants and animals
(natural presence of organisms) in particular localities is not simply a matter
of chance. Their presence is due to factors that make up the environment, i.e.;
biotic (biological or living) and abiotic factors (physical and non-living).
An ecosystem is made up of communities.
BIOTIC FACTORS
Biotic factors are the living components in the environment. They can
either be population or community factor
Population
factors include
-Population density; The number of organism in
a given area.
- Dispersion: the geographical distribution of organisms in an area.
- Age
structure: the distribution of population according to age
- The
ratio of mules to females
-The
number of births
- The
number of deaths
-Population
growth: the rate at which the number of organism is increasing.
Community factors include: Food chain and food webs, these are feeding
relationships that represent flow of energy and recycling of nutrients in a
community.
Abiotic
component.
1. Climatic factors
2. Topographic factors
3. Edaphic factors
Climatic factors
(1) Light; Main source is the sun.
Green plants, green algae and photosynthetic bacteria in the formation of food
use light. The rate of photosynthesis
depends on the quality and intensity of light. The best shades of light are
blue and red.
Distribution of
organisms in relation to light;
-Aquatic; Plant growth is
confined to surface layer due to limitation of light pevet ration.
-Only species which can
tolerate dim light are found on the floor of rain forest or deep in the water
bodies.
-Most animals use daylight
to obtain their food.
-Photoperidism (the number
of daylight hours) influences the flowering of wide variety of plants and
breeding of a number of animal species.
*Measurements
1.
Light intensity using Photographic light
meter
2.
Light
penetration water using seechi disc
2. Temperature. Affects the rate of enzyme
catalysed reactions, i.e. influence almost all activities of plant and animals,
e.g. respiration, photosynthesis, growth, evaporation,
transpiration/transportation, and decomposition
*Distribution
-Few organisms tolerate
extreme temperature
-Homoitherms- wider
distribution (able to live in most part of the word)
-Poikilotherms- abundant in
tropical and sub-tropical regions where environment temp. is close to their
optimal body temp. e.g. reptiles, amphibians, tsetse flies, anopheles mosquito
*Measurements; using Thermometer
3. Wind and air current; Wind is the
moving air. Mostly influence plants, i.e. Strong wind can uproot or breakdown
trees. Airs current modify the temperature and humidity of the air, increases
the rate of transpiration and evaporation.
Effects of wind;
-Cooling effect in hot
season.
-Causes soil erosion
-Strong wind can uproot or
break trees
-Helps in aeration in water
bodies
-Rainfall formations
-Formation of sand dunes in
deserts which act as habitat for some animals
-Affect distribution; most
organism prefer sheltered habitats against strong wind.
-Pollination of plants
-Dispersal of seeds, spores,
and animals.
*Measurement;
-Wind speed using Anemometer
-Wind direction using Wind vane
-Wind strength using wind sock
4. Humidity; Amount of water vapour in
the atmosphere. When there is a lot of water vapour, the humidity is high.
Relative
humidity; is the amount of water vapour the air
can hold at a given temperature. Humidity affects the of transpiration and
evaporation, i.e. Low humidity increases the rate. Humidity is affected by
temperature and wind.
Measurement; Humidity using Hygrometer. (wet and dry bulb hygrometer)
5. Rainfall; Is the main source of soil
water used by terrestrial plants and animals. The amount of rainfall determines
the type of vegetation found in the area. Water is the most abundant and a very important component
of the bodies of plants and of animals.
* Distribution of
organisms
-Areas with high rainfall (tropical rain
forests) support many plants which in turn support many herbivores and
carnivores
-Areas with scarce rain (desert) few plants
and few animals can survive (only organisms with special adaptation can
survive)
*Measurement; using Rain gauge
*Effects of rainfall
-Increases relative humidity
-Increases turbidity
(cloudiness) of water bodies.
-Cause rivers and lakes to
swell.
-Lowers temperature by
evaporation of water from soil.
-May cause floods hence
destroy habitats of some organisms
-Forms puddles and small
ponds, i.e. Habitats for some organisms like mosquitoes and algae.
-Cause soil erosion in areas
with little or no vegetation cover.
*Importance of water
-Is a solvent in which all
biological reactions takes place.
-Is a solvent in which
transports of nutrients, gases, waste products takes place in organisms.
-Raw material for photosynthesis.
-Dissolve minerals in the
soil for early absorption.
-Regulates body temperate.
-Responsible for turgidity
of plants cells, hence maintenance of erect posture.
-Habitat for many organisms
(aquatic life)
-Helps in dispersal of
seeds.
6. Atmospheric pressure. Is the pressure
exerted by atmosphere upon the earth. In high altitudes atmospheric pressure is
low, this means also low concentration of Carbon dioxide and Oxygen,
*Distribution of
organisms
Oxygen needed for
respiration and Carbon dioxide is needed for photosynthesis. High altitudes
limit the number of organisms due to low concentration of such gases.
*Measurement; using Barometer
Topographic factorsl/ Geological factors
These are
factors that are related to the structure of the earth’s surface, i.e. altitude
and configuration the of earth’s surface.
i. Altitude; Is the height above level.
As altitude increases the temperature of gases also fall. Temperature Falls by
approximately 5 0C per 1000 meters. These affect the distribution of
organism.
ii. Slope;(gradient); Steep
slope-water flows faster
-Penetration of water in the soil is low
-Soil erosion is greater
These eventually affect the
growth of plants and presence of other organisms.
iii. Exposure; The degree to
which organisms are not protected from such climatic factors such as rainfall,
sunshine and wind. Most organisms prefer sheltered area.
-Lee side of a mountain
receives little rain than windward side of the mountain.
Edaphic factors
Are the properties of the soil that influence the
distributions of living organisms. The soil is a substratum in which living
organisms are found. Soil provides
plants with water, mineral salt, and anchorage. So soil influence distributions
of plants, which also influence the distributions of animals and other
organisms.
The Edaphic factors (soil properties) that influence distribution
of organisms are;
i. Soil textures; Is determined
by the size of soil particles and humus content. We have clay soils (very small
particles) silty soil (median), Sandy
ii. Soil pH; Acidity or
alkalinity of the soil affect the type of living organisms in the soil. Acid
soils are infertile; i.e. conifers grow best in acidic soil. Grasses grow best
in alkaline. Nitrifying bacteria like alkalinity.
iii. Mineral salts; Type of
vegetation depend on the presence of type of nutrients available.
iv. Water content; Soil water is
found in the space between soil particles. All mineral elements are absorbed by
plants as solution in water.
-Some plants grow best in
water logged areas e.g. Rice.
v. Humus content; Humus is decomposition of plants and animals through action of saprophytic
organisms. Humus provides the soil with nitrogen, phosphorus, calcium and
potassium. Humus help aeration and drainage of the soil (Retain moisture).
Humus can be added to the soil as farmyard manure, compost (garden refuse).
vi. Air content. Provide plant roots and other organisms in the soil with necessary
oxygen for respiration. Provides oxygen and for the nitrifying bacteria and
nitrogen fixing organisms.
vii. Living organisms in the soil. Soil is a home for different
organisms like bacteria, fungi, worms, termites, beetles and snails. These
organisms help in decomposition, nitrogen fixation, aeration and drainage in
the soil
Biotic factor
Refer to the influence of other living organisms to the population.It includes availability of food , predators parasites and competition for basic needs such as food and shelter
Biotic environment of an
organism is the various organisms that surround and interact with that
particular organism. The organisms can be of the same species as well as those
of different species. Main biotic components of an ecosystem are producers, consumers and decomposers. The
distribution and abundance of any living organism depend on its interaction
with other living organisms. This interaction can be;
i Availability of food.
\Populations or communities will thrive in places with adequate food supply
ii. Competition; Organisms usually compete
for limited resources such as food, space, light, water and mates. When such
competition is between members of the same species is called intraspecific competition. e.g. Grasshoppers among themselves in their niche.
When it is between members of different species is called Interspecific competition e.g. lizard and toad competing for grasshopper as
source of food. In these competitions the organisms with suitable structural
and behavioural adaptations survive while those without die or migrate.
-This observation led a
Russian scientist, G.F.Gauze to formulate a principle called; competitive
exclusion principle which states that; “Two different species
can not occupy the same ecological niche and co-exist” For two related
species to co-exist in the same habitat (i.e. ecological niche) they must use
slightly different source of food or be active at different times e.g. sheep
are grazers and goats are browsers.
iii. Predation; Is a
relationship where by one organisms kills another and feed on the whole or part
of the prey. Grazers are herbivorous
that feed on plants. Predators are carnivorous
that feed on other animals, e.g.; lion, pitcher plant.
-Predators maintain the population of the prey at a more or less constant
level through a negative feed back mechanism e.g. increases in number of
predators leads to decrease in no. of prey hence lead to starvation and death
of predators in turn this will lead to increase in no. of prey.
*Adaptation of
predators;
-Sharp claws and canine
teeth
-Highly developed sense of
sight and smell
-Fast running or flight
(birds)
-Camouflage-body colour
similar to that of surroundings e.g. chameleon
-Strong forelimbs (and
modified beaks and feet in birds)
-Venom that kills or
paralyse the prey e.g. snakes, spiders scorpions
*Adaptation of the
prey to minimise Predation
-Fast running- antelopes
-Camouflage-body colour
similar to that of surroundings e.g. chameleon
-Some graze in large herds
to avoid Predation, e.g. buffaloes
-Mimicry-some resemble
inedible and inanimate objects or unpalatable organisms e.g. walking stick
insect resemble dry twigs and some moths resemble bees
Comouflage refers to the physical similarity between the organism and its habitat
Importances
Enable organism to conceal itself in order to avoid predators or to approach its prey.Example chameleons and stick insects
-Porcupines has pines.
-Insects lay many eggs to
increase chance of survival
iii. Parasitism; Is an association where by
one organism (parasite) obtain food and sometimes shelter from another organism
(host). The host is usually harmed. Parasites are of two types:
-Ectoparasites: Live on the body
surface of the host, e.g. ticks, mosquitoes.
-Endoparasites: Live inside
the host, e.g. plasmodium, filaria worms
iv. Symbiosis=mutualism: Is an
association of organisms from different species where all members benefit from
each other, e.g. leguminous plants and nitrogen fixing bacteria, Ruminants and
cellulose digesting bacteria, flowering plants and pollinators (insects),
Lichen (association of fungus and blue green algae)
v. Commensalisms: Is an association of
organisms from different species in which one of the organism (Commensal) gains
while the other neither loses nor gains e.g. cattle and the white cattle egret.
vi. Habitat: Some organisms act as
habitat for other organisms, e.g. insects and plants, birds/monkeys and trees,
parasites and their hosts.
vii. Pollination and dispersal: Some organisms
(insects, birds, and mammals) act as agents of pollination and dispersal for
other organisms like plants.
viii. Man’s activity. Man is the most influential
biotic factor in most habitats. He has transported plants and animals from
their places of origin and successfully managed to grow then elsewhere.
Man also contributed to environmental
degradation through deforestation, over grazing, over cultivation, over fishing
and pollution.
interaction of living and non-living things
The interaction of biotic and abiotic components of the environment is important for the completion of natural cycle, the carbon cycle and the nitrogen cycle.
The water cycle
Water cycle refers how water circulates in the environment.
 |
| Fig Water cycle |
Water cycle
In the water cycle
• Ground water and run-off flow into streams and rivers
• The streams and rivers flow into lakes and ocean
• Water evaporates into the atmosphere from water bodies such as oceans and from plant through transpiration.
• The evaporated water precipitates to form water vapour. Water vapour condenses to form clouds.
• Wind causes clouds to move eg. From above the ocean to above the land.
• Rain falls and is absorbed by plants or forms ground water and run-off. The cycle thus begins again.
The Carbon Cycle
• Carbondioxide from the atmosphere is absorbed by plants and used for photosynthesis. These plants serve as food for herbivores which are in turn eaten by carnivores.
• When plants and animals die, in turn microorganism cause decomposition and carbon dioxide is released into the atmosphere.
• Fossilization of plants and mineral results in the formation of fossil fuels such as coal, natural gas and oil when these fuels are burnt they release carbon dioxide into the atmosphere.
• Respiration of living things also releases carbon dioxide into the atmosphere.
• Volcanic activity is another source of carbon dioxide in the atmosphere.
• The carbondioxide is absorbed by plants then the cycle starts again.
The nitrogen cycle
Nirogen cycle refers to a biochemical cycle in the environment whereby nitrates in the soil are taken up by plant roots and may pass along food chain into animal
- it make up approximately 78%of atmosphere
• Nitrogen- fixing bacteria in the soil and in root nodule of legumes carry out Nitrogen fixation by converting atmospheric nitrogen to nitrates.
• Lighting converts atmospheric nitrogen into nitrate by plants
• Plants use nitrogen compounds to produce plant proteins.
• Plants are eaten by animals use the nitrogen to produce animal proteins.
• When plants and animals die, decomposes such as bacteria and fungi feed on them.
• The decomposers release ammonia gas (NH3) .This gas contains nitrogen. The ammonia is converted into nitrites and then nitrates by bacteria.
• Denitrifying bacteria release nitrogen from nitrates back into the atmosphere.
• Simplified nitrogen cycle
Interdependence
within the community
All living things require
food, which is used to provide energy and materials necessary for growth,
repair and reproduction. The interrelation/interaction in the search for food
forms an Ecosystem or a community.
Ecosystem is natural units where
living and non- living components of the environment interact with each other
to form a stable self-perpetuating unit.
Depending on
the manner in which they obtain their food the organisms in the ecosystem can
be grouped into three groups i.e. producers, consumers and decomposers.
i. Producers: (autotrophs) they use
inorganic materials (CO2) in the atmosphere and in the soil (water
and mineral salts) to make organic compounds through photosynthesis, i.e. in
the presence of sun light. All other organisms in the ecosystem (consumers)
depend directly or indirectly on the food substances made by the autotrophs.
ii. Consumers: Comprise of diverse groups
of animals
*Heterotrophs (herbivorous)
feed directly on plants, they are known as primary consumers.
*Carnivorous: These feed on
the herbivorous, they are called secondary consumers.
*Scavengers: Feed on dead
bodies of herbivorous and carnivorous. They are called tertiary consumers. It
is also possible to have quaternary consumer, which feed on tertiary consumer.
*Omnivore: which feed on
plant of on herbivorous is either a primary or secondary consumer.
iii. Saprophyte
decomposers: These are organisms, which act upon dead and decaying
remains of producers and consumers. The process of decaying release inorganic
materials. For Producers to make new organic compounds they use the inorganic
materials. This way, matter circulates within the ecosystem making it
self-supporting, i.e. stable self-perpetuating unit. Each of the feeding levels
(Energy levels) are called Trophic levels i.e. a stage in
a food chain at which organisms obtain food in the same general manner.
E.g.-producers (green
plants)=First Trophic level
-Primary consumer
(cattle/grasshopper)=Second Trophic level
-Secondary consumer (lion/leopard)=Third
Trophic level. Etc
Note: An organism can occupy a different Trophic levels
depending on what it feeds on, e.g. If a leopard feeds on cats, it is put on 4thTrophic
level as second order carnivore. If the leopard feeds on herbivore (antelope)
it is put in 3rd Trophic level as first order carnivore.
Energy level decreases as it moves from
one trophic level to the next. Only 10% of energy are available for
organisms in the next trophic level.
Where
does 90% of energy go.
(i) Some lost as heat i.e. sweating, urination, evaporation.
(ii) Not all individuals are eaten.
(iii) Some of food is not digested (faeces)
(iv) Not all parts of organisms are eaten, e.g. roots or bones.
Some is locked in
sea-bed or is covered by volcanic activities
Food chains and food webs
show the flow of nutrients and energy
between organisms in the environment. Each organism in a food chain or food web
represents a trophic level.
A trophic level
is the position that an organism occupies in a food chain such as primary producers . secondary consumer
or is the level in which organism have the same feeding habits.
this flow begins with Producers
Producers- are organism that can manufacture their own food.Example green plants
And this is the first trophic level
Producers are eaten by Primary consumer
Primary consumer- make up the second trophic leve Examples are Herbivores eg cow, goats
Secondary consumers- Form the third trophic level
They feed feed on primary consumers Examples Man
Tertiary consumers-Form fourth trophic level, They feed on secondary consumers
Queternary consumers.-
Make up fifth trophi level. They feed on tertiary consumers
Decomposers
Is the final trophic level.Examples bacteria, Fungi
Importances.
These organism fead on dead matter and break it down thereby facilitaitng decomposition
Food chain
s a linear relationship among the organism of a community
in which each organism feeds on and therefore derives energy from the
preceding o the direction of the flow of energy.
or
is the sequence of living things in which each organism is the food of the next one in the sequence.
-It starts with a producer and ends with the top consumer
- arrow are used to show the direction of the flow of energy
-The arrowhead points away from the organism being eaten
Examples
Primary producers such as green plants derives their energy from the
sun.
The chain is shown by arrows. The arrow head points away from the
organism being eaten .
The following are the examples of food chain :-
Food webs:
A food web refers to
several food chain interlinked together.
Naturally, most
herbivores consume more than one kind of plant, omnivores consume more than one
kind of plant or animals and the carnivores consume more than one kind of
herbivore.
Examples of web.
Significance of food chains and food web.
•
Food chains and food web help to maintain an
ecosystem through balancing of the natural environment.
•
Energy
from the sun is utilized and passed on through the trophic level from the first
trophic level to the last trophic level.
•
Food
chains and food webs display a clear picture of dependence between the biotic
components of the environment.