ROUTERA


Chapter 14 Ecosystem

Class 12th Biology Chapter Case Study


Case Study 1: Energy Flow in a Forest Ecosystem

In a temperate forest ecosystem, the energy flow begins with sunlight, which is captured by primary producers like plants and algae through photosynthesis. These primary producers serve as the base of the food chain. Herbivores like deer feed on the plants, and in turn, are consumed by carnivores such as wolves. Decomposers like fungi and bacteria break down dead organic matter, returning nutrients to the soil, completing the cycle.

Questions:

  1. The primary source of energy for the ecosystem described in the case study is:

    • A) Herbivores
    • B) Sunlight
    • C) Carnivores
    • D) Decomposers

    Answer: B) Sunlight

  2. The transfer of energy from primary producers to herbivores in the food chain is an example of:

    • A) Trophic transfer
    • B) Symbiosis
    • C) Nutrient cycling
    • D) Biochemical transformation

    Answer: A) Trophic transfer

  3. The role of decomposers in the forest ecosystem is:

    • A) To consume primary producers
    • B) To break down dead organisms and recycle nutrients
    • C) To control herbivore populations
    • D) To capture solar energy

    Answer: B) To break down dead organisms and recycle nutrients

  4. If herbivores were removed from the ecosystem, the most likely consequence would be:

    • A) An increase in the number of primary producers
    • B) A decrease in the number of carnivores
    • C) A decrease in the energy flow through the ecosystem
    • D) A balanced energy flow with no significant changes

    Answer: B) A decrease in the number of carnivores


Case Study 2: Nutrient Cycling in a Grassland Ecosystem

In a grassland ecosystem, plants like grasses and shrubs absorb nutrients such as nitrogen and phosphorus from the soil. Herbivores like rabbits consume the plants, while carnivores like foxes prey on the herbivores. When plants, herbivores, and carnivores die, decomposers like bacteria and fungi break down the organic matter, returning essential nutrients like nitrogen and phosphorus to the soil, ensuring the continuity of the ecosystem's nutrient cycle.

Questions:

  1. The process by which decomposers recycle nutrients back into the soil is known as:

    • A) Photosynthesis
    • B) Nitrogen fixation
    • C) Nutrient cycling
    • D) Bioremediation

    Answer: C) Nutrient cycling

  2. In the grassland ecosystem, herbivores obtain nitrogen primarily through:

    • A) Direct absorption from the soil
    • B) Feeding on primary producers (plants)
    • C) Carnivory
    • D) Atmospheric nitrogen fixation

    Answer: B) Feeding on primary producers (plants)

  3. The primary function of plants in the ecosystem is to:

    • A) Break down organic matter
    • B) Capture solar energy and convert it into chemical energy
    • C) Regulate the population of herbivores
    • D) Provide shelter for herbivores

    Answer: B) Capture solar energy and convert it into chemical energy

  4. Which of the following elements is most likely to be cycled in the nutrient cycle described in the case study?

    • A) Oxygen
    • B) Nitrogen
    • C) Hydrogen
    • D) Carbon dioxide

    Answer: B) Nitrogen


Case Study 3: Food Web in an Aquatic Ecosystem

In a marine ecosystem, the primary producers are phytoplankton, which are consumed by small herbivorous zooplankton. These zooplankton are, in turn, eaten by small fish like anchovies, which are preyed upon by larger fish such as tuna. At the top of the food chain are apex predators like sharks. When any of these organisms die, decomposers like bacteria break down their bodies, returning nutrients to the water, ensuring a continuous cycle of energy and nutrient flow.

Questions:

  1. The primary producers in the marine ecosystem are:

    • A) Zooplankton
    • B) Phytoplankton
    • C) Tuna
    • D) Sharks

    Answer: B) Phytoplankton

  2. The role of zooplankton in the marine food web is to:

    • A) Consume primary producers (phytoplankton)
    • B) Control the population of large fish
    • C) Decompose organic material
    • D) Serve as the top predators in the ecosystem

    Answer: A) Consume primary producers (phytoplankton)

  3. Apex predators, like sharks, in the food web are:

    • A) The first to consume primary producers
    • B) At the top of the food chain and regulate the population of lower trophic levels
    • C) The main source of energy for herbivores
    • D) Important decomposers in the ecosystem

    Answer: B) At the top of the food chain and regulate the population of lower trophic levels

  4. The breakdown of dead organic material by decomposers in the marine ecosystem primarily results in the recycling of:

    • A) Carbon and oxygen
    • B) Nitrogen and phosphorus
    • C) Energy
    • D) Water

    Answer: B) Nitrogen and phosphorus


Case Study 4: Biomes and their Characteristics

The tropical rainforest biome is characterized by high levels of biodiversity and year-round warmth with abundant rainfall. Plants like trees, shrubs, and vines form dense vegetation layers. The ecosystem supports a variety of animals, including monkeys, birds, insects, and reptiles. These forests play a crucial role in maintaining the Earth’s climate by absorbing carbon dioxide. The tropical rainforest is a dynamic ecosystem that is influenced by both biotic and abiotic factors.

Questions:

  1. The tropical rainforest is characterized by:

    • A) Low biodiversity and cold temperatures
    • B) High biodiversity and consistent warmth with abundant rainfall
    • C) Desert-like conditions with scarce rainfall
    • D) Limited vegetation and seasonal rainfall

    Answer: B) High biodiversity and consistent warmth with abundant rainfall

  2. The role of tropical rainforests in the Earth's climate is most directly related to their ability to:

    • A) Release large amounts of methane
    • B) Absorb carbon dioxide and produce oxygen
    • C) Reflect sunlight away from the Earth
    • D) Store large amounts of nitrogen

    Answer: B) Absorb carbon dioxide and produce oxygen

  3. Which of the following is the most likely abiotic factor that influences the biodiversity in tropical rainforests?

    • A) Temperature
    • B) Species competition
    • C) Predator-prey interactions
    • D) Human activities

    Answer: A) Temperature

  4. The dense vegetation in the tropical rainforest provides:

    • A) Shelter and food for herbivores
    • B) Shelter and food for large carnivores only
    • C) Habitat for a limited number of species
    • D) No significant contribution to biodiversity

    Answer: A) Shelter and food for herbivores


Case Study 5: Ecological Succession in a Pond Ecosystem

A new pond is formed in a region that was previously dry land. Initially, small organisms such as algae and bacteria colonize the pond. As the ecosystem develops, aquatic plants like water lilies and aquatic grasses begin to grow. Over time, larger plants, amphibians, and fish inhabit the pond, and it reaches a more stable state. The process through which the pond ecosystem evolves from bare substrate to a mature community is an example of ecological succession.

Questions:

  1. The initial colonizers of the new pond ecosystem are most likely:

    • A) Amphibians
    • B) Aquatic plants
    • C) Algae and bacteria
    • D) Fish

    Answer: C) Algae and bacteria

  2. The process described in the case study is known as:

    • A) Ecological succession
    • B) Energy flow
    • C) Nutrient cycling
    • D) Food chain development

    Answer: A) Ecological succession

  3. In the pond ecosystem, the arrival of aquatic plants signifies:

    • A) The end of ecological succession
    • B) The establishment of a more complex community
    • C) A decrease in biodiversity
    • D) A disruption of the ecosystem

    Answer: B) The establishment of a more complex community

  4. The stable and mature community that the pond ecosystem reaches is referred to as:

    • A) Pioneer community
    • B) Climax community
    • C) Transitional community
    • D) Decomposers’ community

    Answer: B) Climax community