Experts have designed these Class 7 Science Notes Chapter 9 Life Processes in Animals Class 7 Notes for effective learning.
Class 7 Science Chapter 9 Life Processes in Animals Notes
Class 7 Life Processes in Animals Notes
Class 7 Science Chapter 9 Notes – Life Processes in Animals Notes Class 7
→ Life processes are the fundamental activities that sustain living organisms, including nutrition for energy, circulation for internal transport, respiration for energy release, and excretion for waste removal.
Human Digestive System
The alimentary canal is the continuous tube from the mouth to the anus where food is digested, nutrients are absorbed, and waste is eliminated. It is the body’s food processing pathway.
- Saliva: Saliva is produced by the salivary glands in the mouth. Saliva moistens food, making it easier to chew and Mucus in saliva lubricates the food, aiding its passage down the oesophagus.
- Effect of Saliva: Human saliva contains amylase, an enzyme that begins digesting starch into simpler forms.
- Starch in Potatoes and Chapati: Potatoes and wheat (used in chapati) contain starch naturally, leading to a positive iodine test.
(The iodine solution reacts with starch molecules to form a blue-black complex). - Oesophagus (Food Pipe): Food moves down the oesophagus through rhythmic wave-like muscle contractions.
- Stomach: The stomach’s muscular walls churn and mix the food with gastric juices, further breaking it down physically into a semi-liquid mixture. Hydrochloric acid kills many bacteria ingested with food.
- Small Intestine: The small intestine is the primary site for the complete digestion of carbohydrates, proteins, and fats. It receives digestive enzymes from the pancreas and bile from the liver and gallbladder. Bile, which is mildly basic in nature, produced by the liver and stored in the gallbladder, emulsifies fats, breaking them into smaller droplets.
- The small intestine is specially adapted for absorbing the digested nutrients into the bloodstream and lymphatic system.
- Villi present in small intestine are finger-like projections that further increase surface area and contain blood capillaries, which carries nutrients to different parts of the body.
- Large intestine: The large intestine is the final section of the alimentary canal in humans. Its primary role is to absorb the remaining water and some salts from the undigested food, which helps to solidify it into stool. The stool is then store in the rectum (lower part of the large intestine).
- Anus: Egestion is the removal of undigested food from the body through anus.
Grass-eating animals
- Grass-eating animals such as cows, buffaloes and goats are called as Ruminants.
- Ruminants eat quickly and swallow food without chewing it properly.
- Later, they bring it back into the mouth (cud) and chew it slowly for hours – this is called Rumination.
- Rumen: Stores food; bacteria help start digestion (fermentation).
- Reticulum: Sends partially digested food (cud) back to the mouth.
Birds
- Birds do not have teeth; they swallow whole food.
- Birds don’t chew; they use their beak to pick food and swallow it whole.
Digestive pathway in Birds
- Beak – picks food.
- Oesophagus – food pipe.
- Crop – A storage sac that softens food.
- Gizzard – A muscular part that grinds food with the help of small stones swallowed by the birds.
Respiratory System
- Animals continuously breathe in (inhale) oxygen and breathe out (exhale) carbon dioxide. The process of inhaling and exhaling air is called breathing.
- The respiratory system consists various parts:
Nose – Trachea – Lungs – Alveoli (gas exchange takes place here). - We inhale and exhale air through a pair of nasal openings called nostrils. Nostrils have hair, along with mucus which trap the dust and dirt particles from the air we breathe in.
The air reaches our lungs through windpipe (consists of two branches, which enter the two lungs). Then the air reaches to the small sacs called alveoli. Alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide between the air and the blood takes place.
- The diaphragm is a dome-shaped muscle that helps with breathing. It contracts to let air into the lungs and relaxes to push air out. It also supports posture, speech, and actions like coughing or sneezing.
- Rib cage protects our lungs from external harm, support for breathing and provide structural support.
- Respiration is the process that releases energy from food using oxygen.
Glucose + Oxygen → Carbon dioxide + Water + Energy - Carbon dioxide is released as a waste product during respiration.
- Breathing is a physical process, whereas respiration is a chemical process.
→ Absorption: The digested food gets absorbed by the inner wall of small intestine i.e., Mucosa and pass into the blood vessels, this process is called absorption.
→ Egestion: The process of removal of faecal matter through the anus from time to time is called egestion.
→ Liver: The liver is the largest organ in the body. It weighs between 1-2 kgs. It is a reddish brown gland situated in the upper part of the abdomen on the right side. Liver secretes bile juice.
→ Pancreas: Pancreas is a large cream coloured gland located just below the stomach. The pancreatic juice acts on carbohydrates and proteins and changes them into simpler forms.
→ Fish breathe through gills: Specialized organs for extracting oxygen from water.
→ Gills are located on either side of the fish’s head.
→ Breathing mechanisms in different animals
→ Simple breathing: Directly through their body surface (diffusion). Example – Flatworm.
→ Skin: Some animals use moist skin for breathing. Example- Earthworm.
→ Insects: Insects have network of tubes (tracheal system). Example – Butterflies and ants.
→ Aquatic animals: In aquatic animals gills extract oxygen from water. Example – Fish.- Land Vertebrates: They have lungs (with varying complexity across groups). Example – Humans and dogs.
→ Salivary glands: Salivary glands are a pair of small and branched structures situated in the mouth- cavity. Their secretion is known as saliva which contains starch splitting enzyme called amylase and mucin is for easy swallowing of food.
→ Diaphragm: It is a large muscular sheet forming the floor of the chest cavity.
→ Exhalation: The process of giving out of air that is rich in carbon dioxide is known as exhalation.
→ Gills: Organs of respiration in fishes.
→ Inhalation: The process of taking in of air that is rich in oxygen, into the body is called inhalation.
→ Lungs: Lungs are the main breathing part of our body enclosed in the chest cavity i.e., thoracic chamber.
→ Alimentary Canal: The alimentary canal is the continuous tube from the mouth to the anus responsible for digesting food, absorbing nutrients, and eliminating waste.
→ Mechanical digestion: Breaking down food items physically into smaller pieces so they can be chemically digested more effectively.
→ Saliva: Saliva is the watery liquid in our mouth that helps us chew, swallow, and starts breaking down of food.
→ Secretion: The process by which an animal or plant produces and releases a liquid, or the liquid produced.
→ Oesophagus: The oesophagus is the muscular tube that transports swallowed food from the throat (pharynx) to the stomach.
→ Churn: The stomach muscles chum the food, mixing it thoroughly with digestive juices.
→ Mucus: A sticky, wet liquid produced by glands inside the nose, throat, and other parts of the body that help to protect them.
→ Pancreatic Juice: A clear, alkaline digestive fluid secreted by the pancreas.
→ Villi: The finger-like projections in the small intestine are called villi.
→ Gluten: A sticky substance that is found in grains that we make into flour like wheat, rye.
→ Mind Map:
