Lesson 04
Structure of an Ecology/Components of Ecosystem
Every living organism on earth depends on and interacts with other living and non-living things
to stay alive. Organisms depend on other organisms for food for example, and also depend on
their environment for protection and a place to stay. The particular branch of Science that
studies how organisms interact with other organisms and their environment is called ecology.
Someone who studies these relationships and interactions is called an ecologist.
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Ecology is the study of the interaction between living (biotic) and non-living things
(abiotic) in an ecosystem.
The environment of an organism includes two types of factors, which make up a structure
of an ecosystem: biotic and abiotic.
Biotic and abiotic factors are what make up our surrounding natural world.
Biotic components
The biotic components of an ecosystem are of three types according to the specific roles they
play in operating the ecosystem.
1. Producers (Autotrophs)
2. Consumers (heterotrophs)
3. Decomposers (detritivores)
A. Producers Or Autotrophs
 Organisms that produce their own food through photosynthesis or chemosynthesis are
called Producers or Autotrophs.
 Producers are the autotrophic organisms which can manufacture their own food material.
They capture solar energy to manufacture food from simple inorganic substances like water,
carbon dioxide, salts etc.
 Producers or autotrophs (i.e., plants, algae, plankton and bacteria) convert abiotic factors
into food.
o The most common pathway is photosynthesis, through which carbon dioxide,
water, and energy from sunlight are used to produce glucose and oxygen.
o Examples: Grass, trees, algae, phytoplankton, chemosynthetic bacteria.
Terrestrial Herbivores (Land)
Deer – Eat grass, leaves, and fruits.
Cows – Feed on grass and hay.
Rabbits – Consume grass, vegetables,
and herbs.
Horses – Eat grass, hay, and grains.
Elephants – Feed on leaves, bark, and
fruits.
Giraffes – Eat leaves from tall trees
like acacia.
Zebras – Graze on grasses and
shrubs.
Goats – Eat grass, leaves, and shrubs.
Aquatic Herbivores
(Water)
Manatees (Sea Cows)
– Eat seagrass and
aquatic plants.
Turtles (Some
Species, e.g., Green
Sea Turtle) – Feed on
algae and seagrass.
Rainforest Herbivores
Sloths – Eat leaves
from trees.
Tapirs – Feed on
leaves, fruits, and
aquatic plants.
Macaws (Parrots) –
Eat nuts, seeds, and
fruits.
Desert Herbivores
Camels – Consume desert
plants, grass, and shrubs.
Tortoises (e.g., Desert Tortoise)
– Eat cactus, grass, and
wildflowers.
Gazelles – Graze on desert
vegetation.
B. Consumers Or Heterotrophs
 Heterotrophs – cannot make their own food; acquire energy from other organisms by
ingesting (feeding; consuming) them.
 The term heterotroph is from the Greek “hetero”, which means “others” and “troph”, which
means “food”. The heterotrophs take nutrition from plants or other animals and are unable
to make their own food. Humans, for instance, cook their food but cannot make it
themselves.
 Consumers are of various types depending on the nature of the food they consume. They
are further classified into:
i. Herbivores (Primary Consumers)
o The consumers that eat plants are known as herbivores and are categorized as primary
consumers. Organisms that feed exclusively on plants.
o Examples: Deer, rabbits, caterpillars, zooplankton
ii.
Carnivores (or Secondary Consumers)
o Organisms that feed on other animals.
 Secondary Consumers (Eat Herbivores):
o These feed exclusively on herbivores. The ones that eat the herbivores or the grasseating animals are called carnivores and are categorized as secondary consumers.
o Examples:
 Terrestrial: Snakes (eat rodents), frogs (eat insects), foxes (eat rabbits).
 Aquatic: Small fish like sardines (eat zooplankton), crabs (eat mollusks).
 Tertiary Consumers (Eat Carnivores):
o Tertiary consumers are the apex predators that feed on both secondary and primary
consumers.
o Example:
 Rabbits, consuming grass are an example of primary consumers; snakes,
consuming rabbits are an example of secondary consumers while owls,
consuming snakes are an example of tertiary
Terrestrial Ecosystem (Land)
Frogs – Eat insects like
grasshoppers and beetles.
Snakes – Prey on mice,
rabbits, and birds.
Foxes – Eat rodents, birds,
and insects.
Wild Cats (Lynx, Bobcats) –
Hunt rabbits, birds, and
small mammals.
Spiders – Catch and eat
insects like flies and moths.
Raccoons – Eat insects,
small animals, and fruits
(omnivore).
Hedgehogs – Consume
insects, worms, and small
vertebrates.
iii.
Aquatic Ecosystem (Water)
Small Fish (e.g., Sardines,
Anchovies) – Feed on plankton and
smaller fish.
Jellyfish – Eat plankton and small
fish.
Crabs – Consume mollusks, worms,
and other small animals.
Seals – Eat fish, squid, and
crustaceans.
Octopuses – Feed on fish, crabs,
and shellfish.
Dolphins (Some Species) – Eat fish
and squid but can also act as
tertiary consumers in some cases.
Rainforest Ecosystem
Monkeys (Certain Species)
– Eat insects along with
fruits and nuts.
Ocelots – Small wild cats
that hunt birds, rodents,
and reptiles.
Tree Frogs – Feed on
insects like ants and flies.
Toucans – Eat small lizards,
insects, and fruits
(omnivore).
Desert Ecosystem
Lizards (e.g., Monitor Lizards,
Geckos) – Eat insects, small
mammals, and other reptiles.
Scorpions – Hunt and eat
insects and small lizards.
Coyotes – Feed on rodents,
birds, and insects.
Omnivores
o Organisms that consume both plants and animals. These eat both plant-based and
animal-based food sources
o Omnivores which feed on both flesh and plants are also included in this category.
o Examples:
 Terrestrial: Bears (eat berries and fish), raccoons (eat fruits and small animals), some
birds (eat insects and seeds).
 Aquatic: Certain species of fish (eat algae and smaller fish).
Terrestrial Omnivores (Land)
Bears – Eat fish, berries, honey, and
plants.
Humans – Consume meat,
vegetables, fruits, and grains.
Raccoons – Eat fruits, insects, small
animals, and garbage.
Pigs – Feed on roots, fruits, insects,
and small animals.
Dogs (Some Species, e.g., Foxes,
Wolves) – Eat small animals, fruits,
and plants.
Hedgehogs – Consume insects,
worms, and berries.
Squirrels (Some Species) – Eat nuts,
fruits, and small insects.
iv.
Aquatic Omnivores
(Water)
Certain Fish (e.g.,
Piranhas, Catfish, Tilapia)
– Eat plants, algae, and
smaller fish.
Turtles (Some Species,
e.g., Box Turtle, Red-Eared
Slider) – Consume plants,
insects, and small fish.
Ducks – Eat aquatic plants,
small fish, and insects.
Crabs – Consume algae,
plankton, and dead
animals.
Lobsters – Eat sea plants
and small marine
creatures.
Rainforest Omnivores
Monkeys (e.g., Capuchin
Monkeys, Baboons) – Eat
fruits, nuts, insects, and
small animals.
Toucans – Consume fruits,
insects, and small lizards.
Sloths (Some Species) –
Feed on leaves, fruits, and
small insects.
Desert Omnivores
Coyotes – Eat rodents, birds,
fruits, and insects.
Lizards (Some Species, e.g.,
Bearded Dragons) – Consume
insects, small animals, and
plants.
Scavengers
 Organisms that feed on dead animals. Consume the carcasses of dead animals.
 Scavengers are animals that consume dead or decaying organisms.
 They play a crucial role in the ecosystem by cleaning up carrion (dead animals) and
recycling nutrients.
Terrestrial Scavengers (Land)
Vultures – Feed on carcasses of dead animals.
Hyenas – Scavenge remains of prey left by other
predators.
Jackals – Eat dead animals and food scraps.
Crows & Ravens – Consume carrion, garbage,
and food waste.
Wolves (Sometimes) – Scavenge from dead
animals when food is scarce.
Bears (Partially Scavengers) – Eat dead fish,
animals, and human waste.
Aquatic Scavengers (Water)
Crabs – Feed on dead fish and
organic matter.
Lobsters – Eat decomposing plant
and animal matter.
Sharks (Some Species, e.g., Tiger
Sharks) – Scavenge dead marine
animals.
Catfish – Consume dead plants and
fish.
Sea Gulls – Eat dead fish, marine
waste, and garbage.
Desert Scavengers
Coyotes – Feed on dead animals in
deserts.
Beetles (e.g., Carrion Beetles) –
Decompose dead insects and small
animals.
Lizards (Some Species, e.g.,
Monitor Lizards) – Eat decaying
meat and animal remains.
C. Decomposers/Microconsumers/Reducers
 Decomposers, are the organisms that break down organic matter from dead plants and
animals into the inorganic components, like carbon and nitrogen, that are necessary for life.
 The inorganic matter then returns to the soil and water as nutrients that can be used by
producers anew, continuing the cycle.
 Decomposers are also called saprotrophs: from the Greek “saprós,” or rotten, because they
feed on rotting organic matter. Examples of decomposers include bacteria, fungi,
earthworms, woodlice, millipede, and some insects.
The Role of Biotic Components in an Ecosystem
Biotic components are central to –
1. Energy Flow – Plants (producers) create energy through photosynthesis, forming the
base of the food chain. This energy is passed on to herbivores like rabbits, then to
carnivores such as foxes.
2. Population Dynamics – Each species in a population interacts within a community.
For example, in a forest habitat, populations of birds, insects, and trees coexist and
depend on one another.
3. Maintaining Balance – Predators, prey, decomposers, and producers work together
to stabilise the ecosystem. Without decomposers like earthworms, dead plants and
animals would pile up, disrupting the habitat.
In summary, biotic factors are integral to the structure, function, and sustainability of
ecosystems. Their interactions and relationships ensure the flow of energy, cycling of nutrients,
and overall health of the environment, which in turn supports life on Earth. Understanding and
preserving these biotic interactions is crucial for maintaining ecological balance and ensuring
the continued provision of ecosystem services.
Abiotic factors in an ecosystem
 The world we live in has many ecosystems – from rivers and lakes to forests and valleys.
Animals, plants and microorganisms inhabits in these ecosystems.
 The non-living things like water, air, soil and rocks are also present in them.
 From an ecological perspective, we can categorize these environmental components into
two types – biotic factors and abiotic factors.
 We shall discover what are abiotic factors in an ecosystem.
 Definition of Abiotic Factors
 Abiotic factors are the non-living components of the ecosystem. These include factors such
as wind, water, sunlight, soil, temperature and humidity.
 Abiotic components can be divided into three main categories:
1. physical,
2. chemical, and
3. climatic factors.
 Abiotic components greatly influence the reproduction, growth and maintenance(survival)
of the living organisms residing in the particular ecosystem. They are equally important as
the biotic or living components to maintain the balance in the ecosystem.
1. Physical Abiotic Components
Physical abiotic factors include sunlight, water, soil, and air, which provide the basic conditions
for life.
a. Sunlight is the primary source of energy in an ecosystem, driving photosynthesis in
plants. More sunlight allows for higher plant growth, while less sunlight limits
vegetation.
👉 Example – In tropical rainforests, strong sunlight supports dense vegetation, while in
deep oceans, limited sunlight restricts plant life to shallow waters.
b. Water is essential for all living organisms. The availability of water determines which
species can survive in a habitat.
👉 Example – Cacti store water to survive in dry deserts, while fish need water with the
right oxygen levels to thrive.
c. Soil provides nutrients to plants and supports land-based ecosystems. Its pH level,
mineral content, and texture affect plant growth.
👉 Example – Acidic soil supports pine forests, while nutrient-rich soil helps crops grow.
d. Air contains gases like oxygen, carbon dioxide, and nitrogen, which are essential for
respiration and plant growth.
2. Chemical Abiotic Components
Chemical factors determine the nutrient composition of ecosystems and include pH levels,
mineral content, and salinity (salt levels in water).
a. pH Levels affect nutrient availability in soil and water.
👉 Example – In acidic lakes, fish struggle to survive due to low oxygen levels.
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b. Minerals in soil, such as nitrogen, phosphorus, and potassium, are essential for plant
growth.
👉 Example – A lack of nitrogen in soil can stunt plant growth, affecting food supply for
herbivores.
c. Salinity influences aquatic life. Some organisms, like saltwater fish, require high salinity,
while freshwater species cannot survive in salty environments.
👉 Example – The Dead Sea has such high salinity that only specialized microorganisms can
survive in it.
3. Climatic Abiotic Components
Climatic factors determine weather patterns and environmental conditions, influencing
biodiversity and habitat formation.
a. Temperature affects metabolic rates, reproduction, and survival.
👉 Example – Cold-blooded reptiles depend on external heat to regulate their body
temperature.
b. Humidity influences plant growth and water availability.
👉 Example – High humidity in rainforests supports lush vegetation, while low humidity in
deserts leads to dry, arid conditions.
c. Wind Speed and Air Pressure shape landscapes and ecosystems.
👉 Example – Strong winds in coastal areas lead to sand dune formation, while wind
patterns in deserts shape shifting dunes.
How Abiotic Factors Work Together
These abiotic components interact to create diverse ecosystems. For example, a hot, humid
climate with nutrient-rich soil supports dense forests, while a cold, dry environment with
rocky terrain forms a tundra. Changes in one factor, such as a rise in temperature or a drop in
rainfall, can disrupt the balance of an entire ecosystem.
The Interaction Of Biotic And Abiotic Factors In An Ecosystem
The interaction between biotic (living) and abiotic (non-living) factors in an ecosystem is
essential for maintaining balance and sustaining life. These interactions determine the survival,
growth, and reproduction of organisms. Here’s how they interact:
1. Energy Flow (Sunlight & Producers)
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Abiotic Factor: Sunlight provides energy.
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Biotic Factor: Plants (producers) use sunlight for photosynthesis to create food, which
supports herbivores and other organisms.
2. Water Cycle (Hydration & Growth)
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Abiotic Factor: Water is essential for all living organisms.
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Biotic Factor: Plants absorb water from the soil, animals drink water, and water helps in
metabolic processes.
3. Soil and Nutrient Cycling
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Abiotic Factor: Soil provides minerals and nutrients.
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Biotic Factor: Plants take up nutrients, decomposers (like fungi and bacteria) break down
dead matter, returning nutrients to the soil.
4. Temperature & Adaptation
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Abiotic Factor: Temperature affects survival and reproduction.
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Biotic Factor: Animals adapt to temperature (e.g., thick fur in cold regions, shedding fur
in summer).
5. Oxygen and Respiration
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Abiotic Factor: Air contains oxygen for respiration and carbon dioxide for photosynthesis.
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Biotic Factor: Animals breathe in oxygen, plants use carbon dioxide for photosynthesis.
6. Climate and Migration
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Abiotic Factor: Seasonal changes, wind, and rainfall patterns affect the environment.
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Biotic Factor: Birds migrate to warmer regions, animals hibernate, and plants shed leaves
in dry seasons.
These interactions create a balanced ecosystem where abiotic factors support life, and biotic
factors modify their environment for survival. If an abiotic factor changes significantly (e.g.,
climate change, pollution), it can disrupt the balance, affecting all organisms in the ecosystem.
Section 1: Ecosystem Components
Scenario:
In a forest, sunlight provides energy to plants, while soil and water help them grow. Deer eat
the plants, and wolves hunt the deer. Fungi break down dead leaves and animals.
1. Which of the following is an abiotic factor in this scenario?
A) Deer
B) Sunlight
C) Fungi
D) Wolves
2. What role do the plants play in this ecosystem?
A) Decomposers
B) Producers
C) Primary consumers
D) Secondary consumers
Section 2: Human Impact & Decomposers
Scenario 4: A farmer sprays pesticides on crops, killing most soil bacteria and earthworms.
1. What is the long-term effect on the ecosystem?
A) Faster nutrient cycling
B) Dead organisms pile up, nutrients trapped
C) Plants grow healthier
D) Herbivores increase
Explanation: Decomposers like soil bacteria and earthworms break down dead organic
matter, recycling nutrients back into the ecosystem. Without them, dead organisms cannot
be properly decomposed, and nutrients become trapped in the dead material.
2. Which organism is most affected by the loss of decomposers?
A) Hawks
B) Flowering plants
C) Grasshoppers
D) All of the above
Explanation: Decomposers are critical for recycling nutrients, which plants need for growth.
Without decomposers, the nutrient cycle is disrupted, affecting the entire food chain. Plants
suffer from nutrient deficiencies, which impacts herbivores (like grasshoppers), which, in turn,
affects higher trophic levels, such as hawks.
Scenario 1: The Wetland Ecosystem
You are observing a wetland ecosystem that includes marshes, aquatic plants, frogs, birds, and
insects. Recently, a large area of wetland was drained to build a housing development,
significantly reducing the available habitat for many species.
1. What is the most direct consequence of draining the wetland?
o a) An increase in the frog population
o b) Loss of habitat for many species
o c) A decrease in the number of aquatic plants
o d) Improved water quality
Explanation: Draining the wetland removes the habitat for species that depend on wetlands,
such as frogs, birds, and insects. This is the most direct and immediate impact.
2. Which group of organisms is most likely to be impacted by the loss of wetland plants?
o a) Decomposers
o b) Primary consumers (herbivores)
o c) Tertiary consumers (carnivores)
o d) Secondary consumers
Explanation: Primary consumers (like herbivores) directly depend on plants for food. The loss of
wetland plants would most severely affect herbivores, which rely on them for survival.
3. What abiotic factor would likely change as a result of draining the wetland?
o a) Soil temperature
o b) Air quality
o c) Water levels and availability
o d) Oxygen levels in the air
Explanation: Draining the wetland reduces the amount of water in the ecosystem, directly
impacting the water levels and availability, which is essential for the species living there.
4. If the wetland ecosystem is destroyed, which of the following would happen?
o a) Birds would find new habitats and thrive
o b) Aquatic life would increase
o c) Biodiversity would decrease
o d) The soil would become more fertile
Explanation: Wetlands support a variety of species, and destroying this habitat would cause a
loss of biodiversity. Many species that depend on the wetland would no longer be able to
survive.
Scenario 2: The Agricultural Ecosystem
You are studying an agricultural ecosystem where crops like wheat and corn are grown. The use
of pesticides has been increased to control pests, but this has led to the decline of beneficial
insects, such as pollinators.
1. What is the most direct effect of pesticide use on the ecosystem?
o a) Increased crop yields and healthier plants
o b) The decline of beneficial insects, such as pollinators
o c) A rise in the number of herbivores feeding on crops
o d) More predators for crop pests
Explanation: Pesticides are designed to kill pests, but they often also harm beneficial insects,
such as pollinators, which are crucial for the reproductive success of many plants, including
crops.
2. How would the decline in pollinators likely impact crop production?
o a) Crops would grow faster without pollinators
o b) Crop yields would decrease due to poor pollination
o c) Crop pests would become less problematic
o d) Pollination would still occur naturally through wind and rain
Explanation: Pollinators, such as bees, are essential for transferring pollen between plants. A
decline in pollinator populations would lead to reduced pollination, lowering crop yields.
3. What is the role of pollinators in an agricultural ecosystem?
o a) They fertilize crops and help increase soil fertility
o b) They help transfer pollen from one plant to another, enabling reproduction
o c) They decompose organic matter, returning nutrients to the soil
o d) They regulate the water cycle by absorbing excess moisture.
Explanation: Pollinators facilitate the fertilization process in plants by transferring pollen, which
is essential for the production of seeds and fruits in many crops.
4. What is the most sustainable way to control pests in an agricultural ecosystem?
o a) Increasing pesticide use
o b) Introducing more herbivores to control pests
o c) Using integrated pest management (IPM), which combines biological, cultural,
and mechanical control methods
o d) Removing all predators from the ecosystem
Explanation: Integrated pest management (IPM) is a sustainable approach that combines
multiple methods (e.g., biological control, crop rotation, physical barriers) to manage pests
while minimizing environmental impact.
These solutions emphasize the importance of pollinators in agricultural ecosystems and
highlight the need for sustainable pest control methods to ensure long-term crop productivity
and ecosystem health.