GRADE 9 Integrated Science LIVING THINGS AND THEIR ENVIRONMENT – Nutrition in animals Notes

• Define nutrition and explain why animals need food.
• Describe types of animal feeding (herbivore, carnivore, omnivore, scavenger, parasite, detritivore).
• Explain the stages of animal nutrition: ingestion, digestion, absorption, assimilation and egestion.
• Give Kenyan examples and show how animals are adapted to their diets.

What is nutrition?

Nutrition is the process by which animals take in food and use it for energy, growth, repair and keeping the body warm. Animals are heterotrophs — they cannot make their own food (unlike green plants that use photosynthesis). Instead they obtain food from other organisms.

Types of feeding in animals

• Herbivores — eat plants. Example: cow, goat, grasshopper, giraffe. (In Kenya: cattle eating grass for milk and meat).
• Carnivores — eat other animals. Example: lion, cheetah, snake.
• Omnivores — eat both plants and animals. Example: human, pig, hyena.
• Scavengers — eat dead animals. Example: vulture, hyena.
• Parasites — live on or in another organism (host) and take food from it. Example: tapeworms in animals, ticks on cattle.
• Detritivores / Decomposers — feed on dead matter and waste, returning nutrients to soil. Example: earthworms, termites, many bacteria and fungi.

Stages of nutrition in animals

1. Ingestion — taking in food through the mouth (or other feeding organ).
2. Digestion — breaking food into smaller molecules. This is mechanical (chewing, grinding) and chemical (enzymes breaking down starch, proteins, fats).
3. Absorption — small food molecules pass into the blood through the walls of the small intestine (or body cells in simple animals).
4. Assimilation — cells use absorbed molecules to make new tissues and to release energy.
5. Egestion — removing undigested waste from the body (faeces).

Simple diagram — human digestive system (overview)

Key enzymes: amylase (starch > sugar), protease (protein > amino acids), lipase (fats > fatty acids + glycerol). The liver and pancreas make important digestive juices.

Adaptations for feeding (Kenyan examples)

• Teeth types: herbivores (cows) have flat molars for grinding; carnivores (lions) have sharp canines for tearing; humans have mixed teeth for an omnivorous diet.
• Ruminants: cows, goats and sheep have a multi-chambered stomach for fermenting plant material with microbes (helps digest cellulose in grasses).
• Long neck (giraffe): reaches high leaves other animals cannot reach.
• Scavengers (vultures): strong stomach acids to digest decayed meat safely.
• Termites: have microbes in their gut to digest wood; they help recycle dead plant matter in soil.

Food chains, food webs and trophic levels

Food chain shows how energy moves from one organism to another. Example:

A food web is many chains linked together. Decomposers return nutrients to soil, supporting producers again.

Why a balanced diet matters (for humans)

• Provides energy for work and school (carbohydrates like ugali, rice, potatoes).
• Helps growth and repair (proteins from beans, meat, fish, milk).
• Vitamins and minerals keep the body healthy (sukuma wiki, fruits).
• Fats give energy and help absorb some vitamins but should be taken in moderation.

Example Kenyan meal: Ugali + sukuma wiki + beans + small piece of fish = carbohydrate + vitamins + protein.

Simple practical activities

1. Observe and compare teeth: look at pictures of a cow, lion and human skull. Note differences and link to diet.
2. Build a simple food chain using local species (e.g., grass → rabbit → eagle) and draw it.
3. Test for starch in food: put a drop of iodine on a small piece of cooked potato or ugali — it turns blue-black if starch is present. (Teacher supervision required.)

Quick review questions

1. Define nutrition in animals.
2. Name five types of feeding in animals and give a Kenyan example of each.
3. List the main stages of nutrition and explain where absorption occurs in humans.
4. Explain one adaptation that helps an animal get its food.