Natural Science Exam Worksheet - Unit 3: Food Chains, Organism Relationships, and Biodiversity

Exam: Unit 3 - Natural Science

#### Task 1: Order the pictures to show the food chain.

The task is to arrange the images in a sequence that represents a typical food chain. Here's how we can do it:

1. Sun: The sun is the primary energy source for all life on Earth. It provides energy for plants through photosynthesis.
2. Corn Plant: Plants use sunlight to produce their own food through photosynthesis. They are producers in the food chain.
3. Mouse: Mice eat plants (like corn) and are primary consumers.
4. Fox or Owl: Both foxes and owls are predators that eat mice. They are secondary consumers.
5. Mushrooms: Mushrooms are decomposers that break down dead organisms and return nutrients to the soil.

Correct Order:
- Sun → Corn Plant → Mouse → Fox/Owl → Mushrooms

#### Task 2: Name and explain the relationship between the following organisms.

##### Predator and Prey
- Relationship: Predation
- Explanation: A predator is an organism that hunts and eats another organism (the prey). For example, a fox (predator) hunts and eats a mouse (prey).

##### Parasite and Host
- Relationship: Parasitism
- Explanation: A parasite lives on or inside a host organism and benefits by deriving nutrients at the host's expense. For example, ticks are parasites that feed on the blood of animals (hosts).

##### Cattle and the Cattle Egret
- Relationship: Commensalism
- Explanation: In commensalism, one organism benefits while the other is neither helped nor harmed. Cattle egrets follow cattle as they graze, eating insects stirred up by the cattle. The egrets benefit, but the cattle are not significantly affected.

#### Task 3: Read and answer.

##### (a) Give two reasons why species become extinct.
1. Habitat Destruction: Human activities such as deforestation, urbanization, and agriculture destroy natural habitats, leaving species without the resources they need to survive.
2. Overhunting/Overfishing: Excessive hunting or fishing of certain species can lead to a rapid decline in their population, eventually causing extinction.

##### (b) Give two examples of things humans can do to preserve biodiversity.
1. Establishing Protected Areas: Creating national parks, wildlife reserves, and marine protected areas helps conserve habitats and protect endangered species.
2. Promoting Sustainable Practices: Encouraging sustainable farming, fishing, and forestry practices reduces the impact on ecosystems and helps maintain biodiversity.

##### (c) Give two examples of animals that are endangered.
1. Tiger: Due to habitat loss and poaching, tigers are critically endangered.
2. Gorilla: Gorillas face threats from habitat destruction, poaching, and disease, making them an endangered species.

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Final Answers:

#### Task 1: Food Chain Order
1. Sun
2. Corn Plant
3. Mouse
4. Fox/Owl
5. Mushrooms

#### Task 2: Relationships
1. Predator and Prey: Predation
2. Parasite and Host: Parasitism
3. Cattle and the Cattle Egret: Commensalism

#### Task 3: Questions
1. Reasons for Extinction: Habitat destruction, overhunting/overfishing.
2. Preserving Biodiversity: Establishing protected areas, promoting sustainable practices.
3. Endangered Animals: Tiger, Gorilla.

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Boxed Final Answer:

\boxed{
\text{1. Sun → Corn Plant → Mouse → Fox/Owl → Mushrooms} \\
\text{2. Predation, Parasitism, Commensalism} \\
\text{3. (a) Habitat destruction, overhunting/overfishing; (b) Establishing protected areas, promoting sustainable practices; (c) Tiger, Gorilla}
}