By Momina Shehzadi | BS Zoology Graduate, Pakistan In this article, we will learn Fungi - Morphology, Reproduction, Physiology and Importance - in simple words with diagram. This topic is very important for BS Zoology and Microbiology students. Fungi are found everywhere around us. They are present in soil, in water, in air, on dead plants, on dead animals, on our food, on our skin and even inside our body. When bread becomes old, green or black spots appear on it. These spots are fungi. When we see mushroom growing after rain, that is also a fungus. When yeast is used to make bread soft, that is also a fungus. Fungi are very different from bacteria and plants. They are eukaryotic organisms. It means their cells have a true nucleus and other membrane bound organelles. They do not have chlorophyll, so they cannot make their own food like plants. They get their food from other living or dead things. That is why they are called heterotrophic organisms. The study of fungi is called mycolog...
By Momina Shehzadi | BS Zoology Graduate, Pakistan
In this article, we will learn about Food Chain and Food Web in simple words with examples from Pakistan. This topic is very important for BS Zoology and BSc Zoology students.
What is food chain?
A food chain is the sequence of who eats whom in an ecosystem to get energy. It shows how energy and nutrients flow from one organism to another. Every living thing needs energy to survive, and this energy comes from food.
In simple words, the Sun is the ultimate source of energy. Green plants use sunlight to make their own food through photosynthesis. Then animals eat plants, and other animals eat those animals. This continuous chain of eating and being eaten is called a food chain.
All food chains start with producers and end with decomposers or top predators. Without food chains, the ecosystem would collapse and life would not continue on Earth.
Trophic levels in food chain
Each step in a food chain is called a trophic level. There are mainly 5 trophic levels:
1. producer - Trophic Level 1
Producers are green plants, algae, and some bacteria. They make their own food using sunlight, water, and carbon dioxide. They are also called Autotrophs. Example: Grass, Trees, Phytoplankton.
2. Primary Consumer- Trophic Level 2
These are herbivores that eat only producers. Example: Cow, Goat, Deer, Rabbit, Grasshopper.
3. Secondary Consumer - Trophic Level 3
These are carnivores or omnivores that eat primary consumers. Example: Frog, Fox, Small Birds, Cat.
4. Tertiary Consumer - Trophic Level 4
These are animals that eat secondary consumers. They are usually larger carnivores. Example: Snake, Eagle, Lion.
5. Decomposers - Trophic Level 5
Decomposers break down dead plants and animals and return nutrients to the soil. Example: Bacteria, Fungi, Earthworm. They are the cleaners of the ecosystem.
The 10% Law of Energy Transfer
This is a very important law given by Raymond Lindeman in 1942. According to this law, only 10% of energy is transferred from one trophic level to the next. The remaining 90% is lost as heat, respiration, incomplete digestion, and other life activities.
For example, if grass has 1000 Joules of energy, then deer will get only 100 Joules, and lion that eats deer will get only 10 Joules. That is why the number of top predators is always less in an ecosystem.
Types of food chain
There are two main types of food chains found in nature:
1. Grazing Food Chain
The grazing food chain is the most common type. It starts with green plants as producers. Energy flows from plants to herbivores and then to carnivores.
It has 4 stages: Producer -> Primary Consumer -> Secondary Consumer -> Tertiary Consumer
Example 1 - Terrestrial Food Chain:
Grass -> Grasshopper -> Frog -> Snake -> Eagle
Example 2 - Aquatic Food Chain:
Phytoplankton -> Zooplankton -> Small Fish -> Big Fish -> Shark
This type of food chain directly depends on solar energy and is very important for energy flow.
2. Detritus Food Chain
The detritus food chain starts with dead organic matter called detritus. This dead matter is eaten by small organisms called detritivores and decomposers.
It does not depend directly on solar energy. It helps in recycling nutrients.
Example:
Dead Leaves and Dead Animals -> Bacteria and Fungi -> Protozoa -> Earthworm -> Birds
In many ecosystems, like forests, about 90% of energy flow occurs through the detritus food chain.
What is food web?
A food web is a network of many interconnected food chains. In nature, no animal eats only one type of food. A rabbit can be eaten by a fox, an eagle, and a wolf. Similarly, a fox can eat rabbit, mouse, and birds.
When we connect all these food chains together, it looks like a web. That is why it is called a food web. A food web is a more realistic representation of feeding relationships in an ecosystem than a simple food chain.
Example of a Food Web in a Grassland:
Grass is eaten by rabbit, grasshopper, and deer.
Grasshopper is eaten by frog and birds.
Frog is eaten by snake.
Rabbit is eaten by fox and eagle.
Deer is eaten by lion.
Snake is eaten by eagle.
All these chains are connected, forming a complex web. If one organism becomes extinct, the food web can still survive because animals have alternative food sources.
Difference between food chain and food web
Features Food Chain Food Web
Definition: A single linear path of energy flow A network of interconnected food chains
Structure: Simple and straight Complex and branched
Stability: Less stable, if one species dies, whole chain breaks More stable, has alternative food sources
Nature :It is a part of food web It is made of many food chains
Example Grass -> Deer -> Lion Multiple chains connected in grassland
Importance of Food Chain and Food Web in Ecosystem
1. Energy Flow:Food chains and food webs show how energy flows from sun to producers to consumers.
2. Nutrient Cycling: They help in cycling nutrients like carbon, nitrogen, and phosphorus from soil to living things and back.
3. Ecological Balance: They maintain balance in nature. If number of deer increases, lions increase and control the population.
4. Understanding Bioaccumulation and Biomagnification: Harmful chemicals like DDT and pesticides enter food chains and become more concentrated at higher trophic levels. This is called biomagnification. Humans as top consumers are most affected.
5. Biodiversity Conservation: By studying food webs, we can understand which species are most important for ecosystem stability.
Food Chain Examples in Pakistan
Pakistan has diverse ecosystems, so food chains are also different:
Desert Ecosystem of Thar:
Cactus -> Desert Rat -> Desert Fox -> Eagle
Forest Ecosystem of Northern Pakistan:
Pine Leaves -> Markhor -> Snow Leopard
Pond Ecosystem in Punjab:
Algae -> Mosquito Larva -> Small Fish -> Kingfisher -> Hawk
What Happens if a Food Chain is Disturbed?
If one link in a food chain is removed, the whole ecosystem is affected. For example, if all snakes are killed, the number of rats and frogs will increase rapidly, which will destroy crops. If all producers are removed, no consumer will survive. Human activities like deforestation, hunting, pollution, and climate change are breaking food chains and food webs, leading to extinction of many species.
Conclusion
The food chain and food web are the backbone of the biosphere. They explain how life is interconnected and how energy sustains all living organisms. A simple food chain shows a single path, while a food web shows the real, complex picture of nature. To protect our environment and biodiversity in Pakistan and around the world, we must protect both food chains and food webs. Saving one species means saving the whole web of life.
FAQs About Food Chain
Q1. Who is at the top of food chain?
Ans: Humans and top predators like Lion, Tiger, Shark and Eagle are at the top of food chain.
Q2. What is the difference between food chain and food web in simple words?
Ans: Food chain is one single line of eating, food web is many food chains joined together.
Q3. What is the first trophic level?
Ans: Producers like green plants are always at the first trophic level.
Q4. What is 10% Law in food chain?
Ans: According to 10% Law given by Raymond Lindeman in 1942, only 10% energy is transferred from one trophic level to the next. Remaining 90% is lost as heat and respiration. Example: If grass has 1000 Joules, deer gets 100 Joules and lion gets only 10 Joules.
Q5: Why is a food chain usually short, with only 4-5 levels?
Ans: A food chain is short because of the 10% Law. At each level, 90% energy is lost as heat and respiration. After 4-5 levels, very little energy is left, so no more levels can survive. That is why there are always more plants than lions.
Q6: What will happen if decomposers are removed from a food chain?
Ans: If decomposers like bacteria and fungi are removed, dead plants and animals will not decay. Nutrients will not return to the soil, plants will not grow, and the whole food chain will collapse. Decomposers are the cleaners of the ecosystem.
Also read previous complete topic ecosystem and its types
Written by Momina Shehzadi from Pakistan. I made these notes for my exams.
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