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ENERGY FLOW IN AN ECOSYSTEM

The sun is the natural source of energy. It is this energy that is trapped by green plants for photosynthesis. This process produces food which is potential energy in chemical form e.g glucose. Therefore, green plants are called producers in an ecosystem.

Green plants are eaten by animals e.g herbivores which the primary Consumers. They in turn are eaten by carnivores, usually referred to as secondary consumers e.g dogs. The secondary consumer is eaten by tertiary Consumer e.g leopard.

When the leopard ides its eaten by a vulture which is referred to as quaternary consumers. These feeding levels, that is producers and consumer levels are referred to as trophic levels. When living organisms die, they are decomposed by bacteria and fungi which are referred to as decomposers. The energy moves from one trophic level to the next i.e producers to the consumers.

Decomposers

Dead bodies of organisms and waste material from their body form a source of energy and nutrients for many other organisms known as decomposers. Most decomposers are bacteria and fungi.

The decomposers breakdown organic materials into simple substances which are made available for re-use by other organisms thus the materials are recycled in the ecosystem. The rate at which decomposers work on substrate differs depending on climate and type of substrate.

Food Chains

Food chain is the linearly representation of the flow of energy from producer to other organisms. It is composed producers, consumers and decomposers. e.g
Producer ----> Primary cionsumer----->secondary consumer---à Decomposers.

Specifics examples rae as follows:

Grass ---> Grashopper-->Bird

Napier grass---> Goat--->human

Kikuyu Grass-->mouse-->snake-->Hawk

Algae-->Mosquito larvae-->tilapia-->Nile perch-->Human

When the decomposers are included in the food chain they are ussualy placed at te end as shown below

Litter-->Earthwort-->Frog-->Snake-->Bacteria and Fungi

Food Webs

In a community where populations live and interact, simple food chains rarely exist. Most associations concerned with energy flow are made of several interconnecting food chains forming food webs.

An example of food web: the African savannah grass Cymbopogon afronardus is eaten by termites which are in turn eaten by chicken. The chicken are the consumed by human beings. This so far, constitutes a simple food chain. The relationship between this grass and other organisms, however, is not as simple. The same grass is also eaten by grasshopper and sheep. At various stages other consumers are involved forming a food web.

Ecological Pyramids

The efficiency of transfer from one trophic level to another can be summarized diagrammatically in form of pyramids. These pyramids give pictorial representation of feeding relationships and energy flow in an ecosystem. They are useful on comparing different ecosystems, showing seasonal variations in an ecosystem or change in components of an ecosystem. T

There are three types of pyramids;

Pyramid of numbers

In a natural ecosystem there is progressive decrease in the numbers of organisms constituting any trophic or feeding level in a food chain. The greatest in number are the producers followed in decreasing order by primary consumers, secondary consumers, tertiary consumers and atleasts of all quaternary consumers.

When this numbers are drawn to scale the above food relationships produce a pyramid-shaped histograph or pictograph called Pyramid of numbers.
Construction of Pyramid of Numbers

1. Use data collected or provided

2. From the data identify and draw the most suitable food chain.

3. Indicate the numbers at each trophic level in the food chain.

4. Choose a suitable scale of data.

5. Using the choosen scale draw a horizontal rectangular bar to represent the number of producers as the base of the pyramid.

6. Progressively draw the horizontal bars of the other trophic levels in their ascending order.

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FACTORS OF ECOSYSTEM

Abiotic factors

Light

The sun is the main source of energy to all life on earth. Green plants and photosynthetic bacteria need light to manufacture their food. Animals depend on plants for food.

Light affects living things in terms of intensity, quality and duration. Light intensity and quality affects photosynthesis, flowering and germination of plants while in animals affects migration, hibernation and reproduction.
A photographic light meter is used to measure light intensity while the seechi disc measures light penetration in water.

Temperature

Biochemical processes of most organisms function effectively within a narrow range of temperature. Temperature varies due to seasons, altitude, latitude and also diurnally especially in hot deserts.

This therefore affects the distribution of organisms in a habitat. Temperature variations influence the distribution of organisms more in terrestrial habitats than aquatic habitats. Living organisms must develop necessary physiological and behavioral adaptations to cope with extremes of temperatures.

Atmospheric Pressure

The atmosphere has a definite weight and so it exerts pressure on the earth. On the surface of the earth, atmospheric pressure varies with altitude. Variations I atmospheric pressure affects the amount of Oxygen available for respiration and of carbon (IV) oxide for photosynthesis. Thes two gases affect the distribution of organisms.

Humidity

It refers to the amount of water vapour in the atmosphere. When humidity is high there is much water vapour and vice versa.

Humidity affects the rate at which water evaporates from the surface of organisms such as in transpiration or sweating. This in turn affects their distribution on earth. Paper Hydrometer is used to measure or a wet and dry bulb hydrometer

Wind

Wind is moving air. It increases the rate of water loss from the organisms, therefore affecting their distribution.

Wind is also important in formation of rain. In deserts winds form sand dunes which can be habitats for other organisms.

Wind causes wave formation in lakes and ocean, which enhance aeration of water in this water bodies.

Trees in areas experiencing a strong winds may have stunted growth and distorted growth.

Wind also disperses spores and seeds hence influence disposal and migration of flying animals

Wind wafts scent hence determines the positioning of hinting animals with respect to their prey in a habitat.

A wind vane or windsock is used to determine the direction of prevailing wind.

Anemoter is used to measure the speed of wind.

Salinity

It refers to the salt concentration of water, causing a division of the aquatic environment into marine, estuarine and fresh water.

Saline conditions immediately outside the body of organism pose the problem of water loss from the body to the environment. Only animals with suitable osmoregulation adaptations can occupy such habitats.

Salinity can be determined by calculating percentage of of salts on water or by the acid-base titration method.

pH ( Hudrogen ion Concerntration)

pH is is the measure of how acidic or alkaline water is in aquatic animals or soil solution. It influences the distribution of plants and animals in soil and fresh water ponds. Some plants drive well in acidic conditions while others in alkaline conditions.

The pH of a soil can be altered by leaching fertilizers’ applied or soil exhaustion. pH is expressed in terms of Ph scale by use of BDH universal indicator solution or paper and pH meter.

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What is a biome?

Biomes are very large ecological areas on the earth’s surface, with fauna and flora (animals and plants) adapting to their environment. Biomes are often defined by abiotic factors such as climate, relief, geology, soils and vegetation.

A biome is NOT an ecosystem, although in a way it can look like a massive ecosystem. If you take a closer look, you will notice that plants or animals in any of the biomes have special adaptations that make it possible for them to exist in that area. You may find many units of ecosystems within one biome.

There are five major categories of biomes on earth. In these five, there are many sub-biomes, under which are many more well defined ecosystems.Let us take a quick look at each of these biomes below:
(Click Green Buttons Below)

The Desert Biomes: They are the Hot and Dry Deserts, Semi Arid Deserts, Coastal Deserts and Cold Deserts.

The Aquatic Biomes: Aquatic biomes are grouped into two, Freshwater Biomes (lakes and ponds, rivers and streams, wetlands) and Marine Biomes (oceans, coral reefs and estuaries).

The Forest Biomes: There are three main biomes that make up Forest Biomes. These are the Tropical Rainforest, Temperate and Boreal Forests (also called the Taiga)

The Grassland Biomes: There are two main types of grassland biomes: the Savanna Grasslands and the Temperate Grasslands.

The Tundra Biomes: There are two major tundra biomes—The Arctic Tundra and the Alpine Tundra.

Biomes play a crucial role in sustaining life on earth. For example, the Aquatic biome is home to millions of fish species and the source of the water cycle. It also plays a very important role in climate formation. The terrestrial biomes provide foods, enrich the air with oxygen and absorb carbon dioxide and other bad gases from the air. They also help regulate climate and so on.

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Scales of Ecosystems

Ecosystems come in indefinite sizes. It can exist in a small area such as underneath a rock, a decaying tree trunk, or a pond in your village, or it can exist in large forms such as an entire rain forest. Technically, the Earth can be called a huge ecosystem.

The illustration above shows an example of a small (decaying tree trunk) ecosystem

To make things simple, let us classify ecosystems into three main scales.

Micro:
A small scale ecosystem such as a pond, puddle, tree trunk, under a rock etc.

Messo:
A medium scale ecosystem such as a forest or a large lake.

Biome:
A very large ecosystem or collection of ecosystems with similar biotic and abiotic factors such as an entire Rainforest with millions of animals and trees, with many different water bodies running through them.

Ecosystem boundaries are not marked (separated) by rigid lines.
They are often separated by geographical barriers such as deserts, mountains, oceans, lakes and rivers. As these borders are never rigid, ecosystems tend to blend into each other. This is why a lake can have many small ecosystems with their own unique characteristics. Scientists call this blending “ecotone”

Ecosystems can be put into 2 groups. If the ecosystem exists in a water body, like an ocean, freshwater or puddle, it is called an aquatic ecosystem. Those that exists outside of water bodies are called terrestrial ecosystems.

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What is an Ecosystem?

An ecosystem includes all of the living things (plants, animals and organisms) in a given area, interacting with each other, and also with their non-living environments (weather, earth, sun, soil, climate, atmosphere). Ecosystems are the foundations of the Biosphere and they determine the health of the entire earth system.

In an ecosystem, each organism has its own niche or role to play.

Consider a small puddle at the back of your home. In it, you may find all sorts of living things, from microorganisms to insects and plants. These may depend on non-living things like water, sunlight, turbulence in the puddle, temperature, atmospheric pressure and even nutrients in the water for life. (Click here to see the five basic needs of living things)

This very complex, wonderful interaction of living things and their environment, has been the foundations of energy flow and recycle of carbon and nitrogen.

Anytime a ‘stranger’ (living thing(s) or external factor such as rise in temperature) is introduced to an ecosystem, it can be disastrous to that ecosystem. This is because the new organism (or factor) can distort the natural balance of the interaction and potentially harm or destroy the ecosystem. Click to read on ecosystem threats (opens in new page).

Usually, biotic members of an ecosystem, together with their abiotic factors depend on each other. This means the absence of one member or one abiotic factor can affect all parties of the ecosystem.

Unfortunately, ecosystems have been disrupted, and even destroyed by natural disasters such as fires, floods, storms and volcanic eruptions. Human activities have also contributed to the disturbance of many ecosystems and biomes.

Ecosystem goods and services
This is the extremely vital life-support services ecosystems provide to human life, its well-being and future economic and social development. For example: The benefits ecosystems provide include food, water, timber, air purification, soil formation and pollination.

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Levels of organization in an ecosystem

To understand the levels of belonging in an ecosystem, let us consider the diagram below.

Individual, Species, Organism:
An individual is any living thing or organism. Individuals do not breed with individuals from other groups. Animals, unlike plants, tend to be very definite with this term because some plants can cross-breed with other fertile plants.
In the diagram above, you will notice that Gill, the goldfish, is interacting with its environment, and will only crossbreed with other gold fishes just like her.

Population:
A group of individuals of a given species that live in a specific geographic area at a given time. (example is Gill and his family and friends and other fishes of Gill’s species) Note that populations include individuals of the same species, but may have different genetic makeup such as hair/eye/skin colour and size between themselves and other populations.

Community:
This includes all the populations in a specific area at a given time. A community includes populations of organisms of different species. In the diagram above, note how populations of gold fishes, salmons, crabs and herrings coexist in a defined location. A great community usually includes biodiversity.

Ecosystem:
As explained in the pages earlier, ecosystems include more than a community of living organisms (abiotic) interacting with the environment (abiotic). At this level note how they depend on other abiotic factors such as rocks, water, air and temperature.

Biome:
A biome, in simple terms, is a set of ecosystems sharing similar characteristics with their abiotic factors adapted to their environments.

Biosphere:
When we consider all the different biomes, each blending into the other, with all humans living in many different geographic areas, we form a huge community of humans, animals and plants, and micro-organisms in their defined habitats. A biosphere is the sum of all the ecosystems established on planet Earth. It is the living (and decaying) component of the earth system.

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1.

Which of these do plants produce?

1. soil

2. water

3. oxygen

4. minerals

2.

What did Charles Darwin give to science?

1. Theory of Revolution

2. Theory of Evolution

3.

The exchange of energy that occurs in an ecosystem can be represented as a                .

1. timeline

2. energy map

3. food web

4.

Organisms in this phylum are vertebrates.

1. Chordata

2. Worm

3. Cnidaria

4. Mollusca

5.

break down dead plants and animals.

1. decomposers

2. producers

3. consumers

4. prey

6.

The sequence of organisms through which the energy flows is called a                .

1. food chain

2. food web

7.

“Nature’s recyclers” are referred to as                .

1. decomposers

2. consumer

3. producer

4. predator

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biology

1.

A gradual change in an ecosystem, sometimes occurring over hundreds of years is a                          .

2.

A food chain begins when

1. an animal eats another animal.

2. an animal eats a green plant.

3. a plant eats an insect.

4. an animal eats the remains of a dead tree.

3.

Imagine that pollution caused all of the plants in an aquatic food chain to die. Would this affect the population of the largest fish?

1. Yes, because the largest fish need to eat plants to supplement their diet.

2. Yes, because all the food energy in the chain comes through the plants.

3. No, because the largest fish are big enough to survive a change in the ecosystem.

4. No, because only the smallest fish depend on the plants for survival.

4.

Plants produce oxygen.

1. True

2. False

5.

The 3 things that plants need for photosynthesis is                 ,                      , and                                   .

6.

This science is the study of all living things, both past and present.

1. geoscience

2. astro-science

3. physical science

4. life science

7.

have skin covered with scales, fins to swim, and gills to breathe.

1. reptiles

2. amphibians

3. fish

8.

What is the name of a animal that only eats meat?

1. carnivore

2. human

3. omnivore

4. herbivore

9.

Which kingdom makes its own food and has a cell wall?

1. Plantae

2. Animalia

3. Fungi

4. Protist