6 Ecology and Environmental Biology
6.3 Ecosystems
Ecosystems
Dr V Malathi
An ecosystem is a community of living organisms such as plants, animals and microorganisms and their interactions with their abiotic (non-living) environment. Ecosystems can vary in size and complexity, from a tiny pond to a vast forest or ocean.
The Biotic and Abiotic factors of the Ecosystem
- Biotic Factors: These are the living parts of an ecosystem and include:
- Producers:are living things that use photosynthesis to create their own food, such as plants and algae.
- Herbivores (plant-eaters), carnivores (meat-eaters), omnivores (plant-and meat-eaters), and
- Consumers: Organisms that eat other living things for energy, including herbivores (plant-eaters), carnivores (meat-eaters), omnivores (both plant and meat-eaters), and decomposers (organisms like fungi and bacteria that break down dead matter).
- Decomposers : These organisms break down dead materials and returns nutrients to the soil.
- Abiotic Factors: These are the non-living elements of an ecosystem, which include:
- Sunlight: The majority of ecosystems rely on sunlight as their main energy source
- Water : is necessary for all living things.
- Soil: Supports a variety of species and gives plants nutrition.
- Climate and temperature :have an impact on whether species can survive and flourish in a given ecosystem.
Energy flow and Nutrient cycling in an Ecosystem
Energy Flow: Producers (plants and algae) use photosynthesis to absorb energy from sunlight that enters ecosystems. After consumers devour plants or other animals, energy is transferred to decomposers, which repurpose nutrients in the environment.
Nutrient cycling is the movement of elements such as carbon, nitrogen, and phosphorus through the environment and living things. In the carbon cycle, for example, carbon is taken up from the atmosphere by plants, passed on to animals when they consume the plants, and then released back into the atmosphere when creatures respire or decompose.
The food chain and food web are models that describe how energy and nutrients move through ecosystems via interactions among organisms.
Food Chain
A food chain is a linear series that illustrates how energy moves across an ecosystem as one organism eats another. Trophic levels are the names given to each stage of the food chain. This is an illustration of a basic food chain:
- Producers: Algae or plants that use photosynthesis to create their own nourishment. (For instance, grass)
- Primary consumers :Herbivores that consume producers are the Primary consumers. (grasshopper, for instance)
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- Secondary Consumers : Carnivores or omnivores that consume herbivores are examples of secondary consumers. (For instance, frogs)
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- Tertiary consumers : Carnivores that ingest secondary consumers are known as tertiary consumers. (for instance, a snake)
- Quaternary consumers :Top predators with few or no natural enemies are known as quaternary consumers. (For instance, hawk)
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A single pathway of energy flow is represented by each link in the chain, but this is usually a simplified picture because few creatures depend on a single food source.
Food Web
A food web is an intricate network of interrelated food chains that shows the different feeding interactions between creatures in an ecosystem. Given that most species participate in several chains and have diverse diets, it offers a more accurate depiction of energy flow.
For instance:
Mice, grasshoppers, and rabbits all consume grass.
Birds and frogs may consume grasshoppers.
Birds and snakes may feast on frogs, while hawks may consume the snake.
This structure resembles a web, demonstrating the multidirectional flow of energy that strengthens and stabilizes the ecosystem. Given that organisms frequently depend on several food sources and act as food for numerous others, a food web more accurately captures the complexity of nature.
Differences Between Food Chain and Food Web
| Aspect | Food Chain | Food Web |
|---|---|---|
| Structure | Linear sequence of energy transfer | Interconnected network of food chains |
| Complexity | Simple, one-to-one relationships | Complex, many-to-many relationships |
| Stability | Less stable, relies on few species | More stable due to diversity |
| Representation | Basic model of energy flow | Realistic model of ecosystem interactions |
Scroll the image slider to know about the interactions among factors of an ecosystem and Components of an ecosystem
Ecosystem Types
Ecosystems can be divided into two categories: aquatic (found in water) and terrestrial (found on land):
Terrestrial Ecosystems
Forests, tundras, grasslands, and deserts are examples of terrestrial ecosystems.
Terrestrial ecosystems are divided into broad groups known as biomes, which include tundra, savannas, tropical rain forests, deserts, coniferous forests, and deciduous forests. The enormous diversity of the different ecosystems within these biomes is obscured when they are grouped into a small number of biome categories. Desert vegetation, for instance, varies greatly. In the Sonoran Desert in the United States, saguaro cactus and other plant life are very abundant, in contrast to the barren rocky desert of Boa Vista, an island off the coast of Western Africa.
Aquatic ecosystems
These can be either marine (such as coral reefs and seas) or freshwater (such as rivers, lakes, and ponds).
Marine ecosystems
These are the most common type of ecosystem. They make up to 75 percent of the Earth’s surface.
These include the shallow ocean, deep ocean water, and deep ocean surfaces (the low depth regions of the deep oceans) Ecosystems.
The deep ocean surface is renowned for the vast amounts of plankton and krill (small crustaceans) that sustain it, whereas the shallow ocean ecosystems feature incredibly biodiverse coral reef ecosystems. Since 40 percent of all photosynthesis on Earth is carried out by phytoplankton, these two habitats are particularly significant to aerobic respirators worldwide. Deep ocean habitats are home to a rich range of marine creatures, however not as many as the other two. Even at the ocean’s bottom, where light cannot pass through the water, such ecosystems can be found.
“Natural Coastal Ecosystems with connections to the Great baririer Reef” by Great Barrier Reef Marine Park Authority, Australian Government is licensed under CC BY-SA 4.0
Freshwater Ecosystems
Only 1.8 percent of the Earth’s surface is home to freshwater ecosystems, making them the rarest. These systems, which are made up of lakes, rivers, streams, and springs, are highly varied and home to a wide range of fish, amphibians, reptiles, insects, phytoplankton, fungi, and bacteria.
Habitat and niche
Habitat and niche are fundamental ecological concepts that describe where organisms live and how they interact with their environment.
Habitat
The physical setting in which a species resides is known as its habitat. It encompasses every element that surrounds and influences an organism’s life, both biotic (living) and abiotic (non-living). The resources required for survival, including food, water, shelter, and space, are provided by a habitat. Coral reefs, rivers, woods, and deserts are a few examples of habitats.
It is an organism’s “address” or location.
For a frog, it can be as small as a pond, while for a whale, it can be as big as an ocean.
The same habitat can be occupied by several species with distinct niches.
Niche
The function or “job” that an organism performs in its environment is known as a niche. It encompasses all of the interactions an organism has with its surroundings, both living and non-living.It describes how an organism lives, behaves, and interacts with its surroundings.
According to the competitive exclusion principle, no two species can spend a significant amount of time in the same habitat occupying the exact same niche.
Through somewhat differing resource use, niche differentiation enables species to coexist in the same habitat.
A niche covers aspects like:
- What the organism consumes and what consumes the organism.
- its habits, such when it hunts or when it reproduces.
- its effects on the ecosystem and other species, such as soil enrichment or pollination.
The niche concept can be divided into two main parts:
- Fundamental Niche: The optimal range of resources and conditions that a species could exploit in the absence of competition is known as its fundamental niche.
- Realized Niche: A species’ actual resources and conditions as a result of competition, predation, and other interactions are known as its realized niche.
Differences Between Habitat and Niche
| Aspect | Habitat | Niche |
|---|---|---|
| Definition | The physical location where an organism lives | The role an organism plays within its ecosystem |
| Function | Provides the resources for survival | Defines the organism’s interactions and activities |
| Uniqueness | Can be shared by multiple species | Unique to each species to avoid competition |
| Example | A forest for a woodpecker | The woodpecker’s role as an insect predator and cavity creator in trees |