Life Processes in Animals — Notes

Written in simple English • Mobile-friendly • Class 7 (Curiosity Science)

1) 20 Most Important Words (Simple meanings in Hindi)

पोषण (Nutrition) — भोजन से ऊर्जा व वृद्धि के लिए पोषक तत्व लेना।

पाचन (Digestion) — जटिल भोजन को सरल भागों में तोड़ना।

आहार नली (Alimentary canal) — मुँह से गुदा तक भोजन की नली।

लार (Saliva) — मुँह का द्रव; स्टार्च को शक्कर में बदलने में मदद।

स्टार्च (Starch) — कार्बोहाइड्रेट; रोटी-चावल में पाया जाता है।

ग्रासनली (Oesophagus) — भोजन को पेट तक ले जाने वाली नली।

पेरिस्टालिसिस (Peristalsis) — नली की लहरदार सिकुड़न-फैलाव जो भोजन आगे बढ़ाए।

पेट (Stomach) — भोजन को मथता और प्रोटीन तोड़ना शुरू करता है।

अम्ल (Acid) — पेट का तेज़ाब; जीवाणु मारता और पाचन में मदद करता।

म्यूकस/श्लेष (Mucus) — पेट की भीतरी परत को अम्ल से बचाता है।

छोटी आंत (Small intestine) — पाचन पूरा; अवशोषण होता है।

यकृत (Liver) — पित्त (Bile) बनाता है।

पित्त (Bile) — अम्ल को निष्प्रभावी करे; वसा को छोटे कणों में बाँटे।

अग्न्याशय (Pancreas) — पाचक रस; कार्बोहाइड्रेट/प्रोटीन/वसा तोड़े।

विल्ली (Villi) — छोटी आंत की उंगली-जैसी उभार; अवशोषण बढ़ाते हैं।

बड़ी आंत (Large intestine) — पानी और कुछ लवण सोखती है।

मलत्याग (Egestion) — अपशिष्ट को मल के रूप में बाहर निकालना।

जुगाली (Rumination) — जुगाली करने वाले जानवर भोजन को फिर चबाते हैं।

पेषणी (Gizzard) — पक्षियों में भोजन पीसने वाला भाग।

श्वसन (Respiration) — ग्लूकोज़ + ऑक्सीजन से ऊर्जा बनना।

🔑 Note: Above meanings are in Hindi. Everything else below is in simple English.

2) Detailed Notes (Simple English)

What are life processes?

Life processes keep living things alive. Main ones: Nutrition, Respiration, Circulation, Excretion, Reproduction.
In this chapter we focus on nutrition (getting food and digesting it) and respiration (using food and oxygen to get energy).

🍽️ Nutrition in Animals

Animals eat different kinds of food: nectar (bees, sunbirds), milk (infants), whole prey (python), tiny particles filtered from water (many aquatic animals).
Food has complex parts — carbohydrates, proteins, fats. These must be broken into simple forms first. This is called digestion.
Digestion happens in a long tube called the alimentary canal (mouth → anus). Special juices break food step by step.

Food Pathway (Human): Mouth → Oesophagus (food pipe) → Stomach → Small intestine → Large intestine → Rectum → Anus

🦷 Mouth (Mechanical + Chemical digestion)

Teeth cut and grind food (mechanical digestion).
Saliva makes food soft and starts chemical digestion. It changes starch (from chapati/rice) into sugar. That is why chewed chapati tastes a little sweet.

Oral hygiene tips: Brush and clean tongue twice a day. Rinse after meals. This prevents tooth decay and bad smell.

🛤️ Oesophagus (Food pipe)

Food moves down by wave-like squeezing and relaxing of the tube. This movement is called peristalsis.

🥣 Stomach

Stomach churns food and mixes it with three things: gastric juice (digests proteins), acid (helps digestion and kills germs), and mucus (protects the stomach wall from acid).
Food becomes semi-liquid here and moves to the small intestine.

How we learned this: Dr. William Beaumont studied digestion through a rare stomach opening of patient Alexis St. Martin (1820s).

🧪 Small Intestine — Digestion finishes & absorption happens

It is the longest part (~6 m). Its lining makes digestive juice. Two helpers add more juices:
Liver makes bile (mildly basic). Bile neutralizes acid from stomach and breaks fat into tiny droplets.
Pancreas makes pancreatic juice (also basic). It further digests carbohydrates, proteins and fats.
Wall of small intestine makes more juice to complete digestion.
The inner lining has many villi (finger-like folds). Villi increase surface area, so digested food can be absorbed into blood quickly.
Blood carries nutrients to all parts for energy, growth and repair.

Health note: In celiac disease, gluten (wheat, barley, rye) harms the small intestine. Gluten-free millets like jowar, bajra, ragi are safer.

🚽 Large Intestine — Water back, waste out

About 1.5 m long, but wider than small intestine.
Absorbs water and some salts. Waste becomes semi-solid stool.
Stool stays in rectum and leaves through anus (egestion).

Gut friends: Helpful bacteria in large intestine digest fiber and make useful substances. Fiber & fermented foods (curd, buttermilk, kanji, pickles, gundruk, poita bhat, etc.) support gut health.

🐄 Do all animals digest food like humans?

Ruminants (cow, buffalo): swallow grass quickly → partial digestion in stomach → bring it back to mouth → chew again (rumination) → swallow for full digestion.
Birds: no teeth; have a muscular gizzard that grinds food (often with small stones they swallow).

🌬️ Respiration in Animals

Breathing = taking air in (inhale) and out (exhale). It is a physical process.
Respiration = oxygen helps break down glucose to release energy inside cells. It is a chemical process.

Word equation: Glucose + Oxygen → Carbon dioxide + Water + Energy

🫁 Human Respiratory System (how we breathe)

Air path: Nostrils → Nasal passages → Windpipe (trachea) → Two bronchi → Many small branches → Alveoli (air sacs) in lungs.
Nasal hairs & mucus trap dust. Lungs lie in the rib cage.
Alveoli are tiny sacs with thin walls and many blood vessels. Here oxygen goes into blood, and carbon dioxide comes out of blood.

Mechanism of breathing

Inhale: Ribs move up & out; diaphragm moves down → chest space increases → air enters lungs.
Exhale: Ribs move down & in; diaphragm moves up → chest space decreases → air goes out.

Inhaled vs Exhaled Air

Gas	Inhaled	Exhaled
Oxygen	~21%	~16–17%
Carbon dioxide	~0.04%	~4–5%

Lime water turns milky faster with exhaled air (more CO₂).

Circulatory link: Blood carries oxygen and nutrients to all parts; collects carbon dioxide and wastes to remove them. The heart pumps blood through blood vessels.

Health caution (Smoking): Damages lungs, raises risk of serious disease, and harms people nearby (passive smoking). Best is to avoid completely.

Breathing practices: Pranayama, deep breathing, and traditional methods like Tummo support lung function and calm the mind (do safely with guidance).

🐟 Breathing in other animals

Fish: breathe with gills; exchange gases with water.
Amphibians (frog): tadpoles use gills; adult frogs use lungs on land and skin in water.
Earthworm: exchanges gases through moist skin.
Birds & mammals: breathe with lungs (structures differ; birds are highly efficient flyers).

🧭 In a Nutshell (Quick Revision)

Digestion breaks complex food into simple parts; absorption happens mainly in small intestine (villi).
Liver (bile) and pancreas (pancreatic juice) help digestion; large intestine takes back water and salts.
Ruminants chew cud (rumination); birds grind food in gizzard.
Breathing brings in O₂ and removes CO₂; respiration releases energy from glucose using O₂.
Gas exchange occurs in alveoli; blood transports gases and nutrients.
Different animals breathe with lungs, gills, skin, or combinations (as per habitat).

Remember & Care

Eat on time; chew well; include fiber and fermented foods.
Brush, clean tongue, rinse; drink enough water.
Do regular physical activity and safe breathing exercises.

Avoid

Overeating and very late meals.
Smoking and passive smoke.
Trigger foods if you have conditions like celiac disease.

Life Processes in Animals — Practice Set

All answers included • Simple English • Chapter 9 (Class 7)

1) One-Word Answer Questions (10)

Process of breaking complex food into simple forms? Digestion
Wave-like movement pushing food in the food pipe? Peristalsis
Finger-like projections in small intestine for absorption? Villi
Balloon-like air sacs in lungs? Alveoli
Greenish fluid from liver that helps digest fats? Bile
Grinding organ in birds? Gizzard
Grass-eating animals that chew cud are called? Ruminants
Removal of undigested waste through anus? Egestion
Main organ of breathing in mammals? Lungs
Organ for gas exchange in fish? Gills

2) Fill in the Blanks (10)

Saliva begins the digestion of ______ by converting it to sugar.
starch
Food moves from mouth to stomach through the ______.
oesophagus
The stomach contains acid, mucus and ______ juice.
gastric
Bile is produced by the ______.
liver
The pancreatic juice helps digest fats, proteins and ______.
carbohydrates
Absorption of digested food mainly happens in the ______ intestine.
small
The percentage of oxygen in inhaled air is nearly ______.
21%
In exhaled air, carbon dioxide is about ______ to 5%.
4%
Tadpoles breathe using ______, while adult frogs use lungs and skin.
gills
The process of producing energy from glucose using oxygen is called ______.
respiration

3) True/False (with Answers & Explanations) — 10

Statement: Digestion ends in the stomach.
False

Most digestion and almost all absorption occur in the small intestine.
Statement: Peristalsis pushes food down the food pipe.
True

Peristalsis is a wave-like contraction/relaxation that moves food along.
Statement: Bile is acidic in nature.
False

Bile is mildly basic (alkaline) and helps neutralise stomach acid.
Statement: Villi increase surface area for absorption.
True

More surface area allows faster and efficient absorption of nutrients.
Statement: Alveoli are found in the small intestine.
False

Alveoli are in the lungs; villi are in the small intestine.
Statement: Ruminants bring back food to chew it again.
True

This is rumination; it helps grind fibrous food like grass.
Statement: Gills are used by birds for breathing.
False

Birds breathe with lungs; gills are for aquatic animals like fish.
Statement: Exhaled air has more carbon dioxide than inhaled air.
True

Exhaled air has ~4–5% CO₂; inhaled air has ~0.04% CO₂.
Statement: Egestion means absorption of food into blood.
False

Egestion is removal of undigested waste through the anus.
Statement: Smoking can harm both smokers and nearby people.
True

Second-hand (passive) smoke also damages lungs and health of others.

4) Very Short Answers (2–3 lines each) — 10

Breathing vs. Respiration?
Breathing is the physical act of taking air in and out of lungs. Respiration is a chemical process in cells where glucose combines with oxygen to release energy, water, and carbon dioxide.
Role of saliva in the mouth?
Saliva moistens food and starts digestion of starch into sugar. It also helps in making a soft bolus for easy swallowing.
How does food reach the stomach?
After swallowing, food passes through the oesophagus by peristalsis—wave-like movements that push food into the stomach.
Two functions of stomach acid?
It helps begin protein digestion and kills many harmful microbes. Mucus protects the stomach wall from the acid.
Why is the “small” intestine the longest part?
It’s called “small” due to smaller width, not length. Its long, coiled length and villi provide a very large area for digestion and absorption.
What do villi do?
Villi are finger-like folds that increase surface area in the small intestine, helping quick absorption of digested nutrients into blood.
How does the diaphragm help breathing?
When it moves down, chest space increases and air enters. When it moves up, chest space decreases and air goes out.
How do fish breathe?
Fish use gills rich in blood vessels to exchange gases with water, taking in oxygen and releasing carbon dioxide.
What is rumination?
In ruminants like cows, partially digested food returns to the mouth to be chewed again (chewing the cud), aiding fiber breakdown.
Why are fermented foods good for gut?
They provide friendly microbes that support digestion and gut health, and help break down some undigested components.

5) Short Answers (3–4 lines each) — 10

Describe the food pathway in the human digestive system.
Food goes: Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Rectum → Anus. Digestion starts in mouth, continues in stomach, and completes in small intestine where absorption happens. Water is reabsorbed in large intestine; waste is egested.
Explain the roles of liver and pancreas in digestion.
The liver produces bile (alkaline) to neutralise acid and emulsify fats into tiny droplets. The pancreas secretes pancreatic juice that digests carbohydrates, proteins, and fats, helping complete chemical digestion.
How does the large intestine help the body?
It absorbs water and some salts from undigested food, forming semi-solid stool. Helpful bacteria also act on fiber. Stool is stored in rectum and removed through the anus.
Outline gas exchange at the alveoli.
Alveoli are tiny air sacs with thin walls and many capillaries. Oxygen diffuses into the blood; carbon dioxide diffuses from blood into alveolar air. This exchange happens quickly due to large surface area and moist thin membranes.
Compare breathing organs of fish, frog, and earthworm.
Fish use gills in water. Frogs: tadpoles use gills; adults use lungs on land and skin in water. Earthworms breathe through moist skin, exchanging gases directly with air.
What is the gizzard and how does it work in birds?
The gizzard is a muscular grinding chamber. Birds often swallow small stones; contractions of the gizzard and grit grind food since birds lack teeth.
List health risks of smoking and passive smoking.
Smoking damages lungs, increases risk of cancer and respiratory diseases, and weakens immunity. Passive smoke harms nearby people—children, elderly, and pregnant women are especially vulnerable.
What happens when exhaled air is bubbled through lime water?
Lime water turns milky because exhaled air contains higher CO₂ (about 4–5%). CO₂ reacts with lime water (calcium hydroxide) to form calcium carbonate, which makes it cloudy.
How does peristalsis aid digestion along the canal?
Peristalsis is rhythmic contraction and relaxation of the canal’s muscles. It pushes food forward, mixes it with digestive juices, and ensures movement even against gravity.
Why is good oral hygiene important for digestion?
Teeth perform mechanical digestion; clean teeth chew better and prevent decay. A healthy mouth supports proper salivary action and reduces infection risk that can disturb overall digestion.

9. Life Processes in Animals