Life Processes in Animals

LIFE PROCESSES IN ANIMALS - Class 7 Science Notes

What are Life Processes?

**Life processes** are essential activities that keep living beings alive. They include:

**Nutrition** - Taking in food and breaking it down for energy

**Respiration** - Converting nutrients into usable energy

**Excretion** - Removing waste from the body

**Reproduction** - Producing new organisms

All animals depend on these processes to survive and function properly.

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9.1 NUTRITION IN ANIMALS

Why Do Animals Need Nutrition?

Animals eat different types of food:

Bees and sunbirds suck flower nectar

Infants drink mother's milk

Snakes swallow their prey whole

Some aquatic animals filter tiny food particles from water

Food contains complex nutrients (carbohydrates, proteins, fats) that must be broken down into simpler forms before the body can use them. This breakdown happens in a long tube called the **alimentary canal** (also called digestive tract).

**Alimentary canal:** Long tube that runs from the mouth to the anus, where food is broken down and absorbed.

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9.1.1 DIGESTION IN HUMAN BEINGS

Digestion is the process of breaking down complex food into simpler forms that the body can use.

STAGE 1: MOUTH CAVITY

**What happens in the mouth?**

1. **Mechanical digestion** - Teeth crush and chew food into smaller pieces

2. **Saliva secretion** - Mouth releases saliva (digestive juice)

**Role of saliva:**

Contains digestive enzyme that breaks down starch (a carbohydrate) into simple sugars

This is why starchy foods like chapati or rice taste sweet when you chew them for a long time

Softens food and mixes with it to make swallowing easier

**Key experiment (Activity 9.1):**

When you chew boiled rice for 30-60 seconds:

**Test tube A** (unchewed rice + iodine) = Blue-black color (starch present)

**Test tube B** (chewed rice + iodine) = No color or very light blue-black (starch broken down into sugar)

This proves that saliva breaks down starch into sugars in the mouth.

STAGE 2: FOOD PIPE (OESOPHAGUS)

**Oesophagus:** A long, flexible tube connecting the mouth to the stomach

**How food moves down:**

Walls of the food pipe contract and relax in a **wave-like motion** (called peristalsis)

This pushes food downward automatically - you don't need gravity!

This is why you can swallow even while standing on your head

STAGE 3: STOMACH

**What is the stomach?**

A muscular bag that churns and partially digests food

**What happens in the stomach?**

1. Stomach walls **contract and relax** to churn food

2. Food mixes with three substances from stomach lining:

**Digestive juice** - Breaks down proteins into simpler forms

**Acid** - Helps break down proteins AND kills harmful bacteria

**Mucus** - Protects stomach lining from acid damage

**Result:** Food becomes a semi-liquid mass (partly digested) and moves to small intestine

**Interesting fact:** In 1822, a man named Alexis St. Martin was shot in the stomach. His wound left a permanent hole that allowed Dr. William Beaumont to observe digestion happening inside the stomach!

STAGE 4: SMALL INTESTINE

**Important facts:**

Called "small" because it is narrow, but it is actually about **6 meters long** - almost twice the height of your classroom!

This is where **most digestion and absorption happens**

**Three sources of digestive secretions in small intestine:**

**1. Liver (secretes bile):**

Bile is mildly basic (alkaline)

**Neutralizes acids** from the stomach (recall neutralization from Chapter 6)

**Breaks down fats** into tiny droplets for easier digestion

**2. Pancreas (secretes pancreatic juice):**

Also basic in nature - neutralizes stomach acids

Breaks down **carbohydrates, proteins, and fats** into simpler forms

**3. Small intestine walls (secrete intestinal juice):**

Further breaks down fats, proteins, and partially digested carbohydrates

**Absorption in small intestine:**

**Absorption** = Process of digested nutrients passing into blood

Inner lining has thousands of **finger-like projections** (called villi) that:

Increase surface area for efficient absorption

Allow nutrients to pass into blood vessels in intestine walls

Blood carries nutrients to all parts of body

**What nutrients do?**

Provide energy for daily activities

Support growth and development

Help body functions work properly

Repair damaged tissues

**Health note:** People with **celiac disease** cannot digest gluten (protein in wheat, barley, rye). This damages the small intestine. Solution: Eat gluten-free foods like jowar, bajra, and ragi (Indian millets).

STAGE 5: LARGE INTESTINE

**Why is it called "large" intestine?**

Not because it's long (it's only 1.5 meters), but because it's **wider than the small intestine**

**What happens here?**

1. Absorbs **water and salts** from undigested food

2. Undigested food becomes **semi-solid waste** called **stool**

3. Stool is stored in lower part called **rectum**

**Health tip:** Eat fiber-rich foods (fruits, vegetables, whole grains) to:

Help large intestine function properly

Make stool easier to pass

Maintain digestive health

**Interesting fact:** Large intestine has helpful bacteria that:

Break down undigested food

Produce essential nutrients

Keep digestive system healthy

Fermented foods (curd, buttermilk, pickles, kanji) are good for these bacteria

STAGE 6: ANUS

**Egestion** = Process of expelling waste through the anus

Body removes waste it doesn't need

Keeps you healthy

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9.1.2 DIGESTION IN DIFFERENT ANIMALS

RUMINANTS (Cows, Buffaloes)

**What is rumination?**

Process where animals chew food, swallow it, partially digest it, bring it back to mouth, and chew again

**Why do cows keep chewing?**

Grass-eating animals are called **ruminants**

They partially chew grass and swallow into stomach

In stomach, **partial digestion** happens

Partially digested food returns to mouth for **gradual rechewing**

Then food goes back down for further digestion

Cows spend about **8 hours a day just chewing**!

**Special stomach structure:** Ruminants have a special chamber called the **rumen** that allows food to be brought back up

BIRDS

**Key difference:** Birds **do NOT have teeth**

**How do birds digest?**

Instead of teeth, birds have a chamber called the **gizzard**

Food is broken down by **contraction and relaxation** of gizzard walls

Birds often swallow **grit (small stones)** which helps grind food in the gizzard

This grinding action replaces the chewing action of teeth

IMPORTANT CONCEPT

**Variations in digestive systems:**

Different animals have different alimentary canal structures and functions because they:

Eat different types of food

Need to adapt to their diet

Have evolved different mechanisms for digestion

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9.2 RESPIRATION IN ANIMALS

Why Is Respiration Important?

Compare how long humans can survive:

Without food: 1 week

Without water: 1-2 days

Without breathing: Only a few minutes!

Respiration is the process of **converting nutrients into usable energy** for the body.

KEY DIFFERENCE: Breathing vs. Respiration

**Breathing** = Physical process of inhaling and exhaling air (mechanical)

**Respiration** = Chemical process of releasing energy from nutrients in cells (biological)

Both are essential and connected!

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9.2.1 RESPIRATION IN HUMANS

THE RESPIRATORY SYSTEM

**Respiratory system** = System of organs that helps us breathe and exchange gases with the body

**Components (in order of air flow):**

**1. NOSTRILS**

Pair of openings where air enters and exits

**Why breathe through nose, not mouth?**

Nostrils have tiny hairs that trap dust and dirt

Hairs + mucus work together as a filter

Clean air reaches lungs

**2. NASAL PASSAGES**

Small passages that air travels through after entering nostrils

Air is warmed and filtered here

**3. WINDPIPE (Trachea)**

Tube connecting nose/mouth to lungs

Divides into **two branches** that enter the two lungs

**4. LUNGS**

Two spongy organs protected by **rib cage** (ribs and bones)

Right lung and left lung

Each lung receives a branch from windpipe

Branches divide into smaller and finer tubes

**5. ALVEOLI** (plural of alveolus)

**Tiny balloon-like sacs** at the end of the smallest branches in lungs

This is where **gas exchange happens**

Oxygen enters blood, Carbon dioxide exits blood

**6. DIAPHRAGM**

**Dome-shaped muscle** below the lungs

Controls breathing movement

HOW BREATHING WORKS

**Activity 9.2: Lung Model**

To understand breathing, make this model:

Use a transparent plastic bottle with removable bottom

Place Y-shaped tube inside (represents windpipe)

Attach deflated balloons to tube forks (represent lungs)

Attach rubber sheet to bottle bottom (represents diaphragm)

**What you observe:**

Pull rubber sheet DOWN → Balloons inflate (like inhaling)

Push rubber sheet UP → Balloons deflate (like exhaling)

THE TWO PARTS OF BREATHING

**INHALATION (Breathing In)**

Ribs move **UP and OUTWARD**

Diaphragm moves **DOWNWARD** (contracts)

Space inside chest **INCREASES**

Air rushes INTO lungs

**EXHALATION (Breathing Out)**

Ribs move **DOWN and INWARD**

Diaphragm moves **UPWARD** (relaxes)

Space inside chest **DECREASES**

Air is pushed OUT of lungs

WHAT DO WE BREATHE OUT?

**Activity 9.3: Testing Exhaled Air**

**Experiment setup:**

Use **lime water** (a chemical that reacts with carbon dioxide)

**Test tube A:** Pass normal air using syringe (air you inhale)

**Test tube B:** Blow your exhaled breath through straw into lime water

**Observations:**

**Test tube A** (inhaled air) = Lime water stays clear (no color change)

**Test tube B** (exhaled air) = Lime water turns **MILKY or CLOUDY**

**What this means:**

**Lime water turns cloudy when it reacts with carbon dioxide**

Therefore: **Exhaled air contains MORE carbon dioxide than inhaled air**

We breathe out the waste gas our body produces

COMPOSITION OF AIR

**Inhaled air contains:**

Oxygen (~21%)

Nitrogen (~78%)

Carbon dioxide (~0.04%)

Other gases (~1%)

**Exhaled air contains:**

More carbon dioxide (4-5%)

Less oxygen (~16%)

More nitrogen and other gases

Water vapor

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IMPORTANT DIAGRAMS TO DRAW

Diagram 1: Human Digestive System

**Label these parts:**

Mouth

Oesophagus (Food pipe)

Stomach

Pancreas

Liver

Small intestine

Large intestine

Rectum

Anus

Diagram 2: Stretched Alimentary Canal

**Show relative lengths:**

Mouth to anus path

Food pipe (short)

Stomach (medium)

Small intestine (about 6 meters - LONGEST)

Large intestine (about 1.5 meters - WIDEST)

Diagram 3: Small Intestine Inner Lining

**Draw and label:**

Intestine wall

Finger-like projections (villi)

Blood vessels inside villi

Note: Increases surface area for absorption

Diagram 4: Ruminant Digestive System

**Label:**

Oesophagus

Rumen (special chamber)

Stomach

Small intestine

Pancreas

Diagram 5: Bird Digestive System

**Label:**

Oesophagus

Stomach

Gizzard (for grinding food)

Intestine

Note: No teeth

Diagram 6: Human Respiratory System

**Label these parts:**

Nostrils

Nasal passages

Windpipe (Trachea)

Left lung

Right lung

Rib cage

Diaphragm

Alveoli (shown as tiny sacs)

Diagram 7: Breathing Mechanism

**Draw two states:**

**Inhalation:** Ribs up/outward, Diaphragm down, Lungs expand, Air in

**Exhalation:** Ribs down/inward, Diaphragm up, Lungs contract, Air out

Diagram 8: Lung Model

**Show:**

Plastic bottle (represents chest)

Y-shaped tube (represents windpipe)

Balloons attached to tubes (represent lungs)

Rubber sheet below (represents diaphragm)

Arrows showing pull and push motion

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SUMMARY TABLE: STAGES OF DIGESTION

| **Part** | **What Happens** | **Secretions** | **Result** |

|----------|-----------------|----------------|----------|

| **Mouth** | Mechanical digestion (chewing) + Saliva action | Saliva (breaks starch to sugar) | Food softened, starch partially broken down |

| **Oesophagus** | Peristalsis (wave-like contraction) | None | Food pushed to stomach |

| **Stomach** | Churning, protein breakdown | Digestive juice, acid, mucus | Food becomes semi-liquid mass |

| **Small intestine** | Complete digestion + Absorption | Bile, pancreatic juice, intestinal juice | Nutrients absorbed into blood |

| **Large intestine** | Water absorption | None | Stool formed (semi-solid waste) |

| **Anus** | Egestion (waste removal) | None | Waste expelled |

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SUMMARY TABLE: GAS EXCHANGE

| **Inhaled Air** | **Exhaled Air** | **Change** |

|-----------------|-----------------|----------|

| 21% Oxygen | 16% Oxygen | Decreased (we use oxygen) |

| 0.04% Carbon dioxide | 4-5% Carbon dioxide | Increased (we produce it) |

| 78% Nitrogen | 78% Nitrogen | No change |

| No water vapor | Has water vapor | Moisture added |

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KEY TERMS TO REMEMBER

**Alimentary canal** - Long tube from mouth to anus for food processing

**Mechanical digestion** - Breaking food into smaller pieces by chewing

**Saliva** - Digestive juice in mouth that breaks down starch

**Peristalsis** - Wave-like muscle contractions that push food

**Digestion** - Breaking down complex food into simpler forms

**Absorption** - Process of nutrients entering blood

**Bile** - Digestive juice from liver that breaks down fats

**Pancreatic juice** - Digestive juice from pancreas

**Villi** - Finger-like projections in small intestine for absorption

**Stool** - Semi-solid waste in large intestine

**Egestion** - Removal of waste through anus

**Rumination** - Chewing of returned food in ruminants

**Gizzard** - Food-grinding chamber in birds

**Breathing** - Physical process of inhaling and exhaling

**Respiration** - Chemical process of releasing energy from food

**Respiratory system** - System of organs for breathing

**Alveoli** - Tiny sacs in lungs where gas exchange happens

**Diaphragm** - Dome-shaped muscle that controls breathing

**Inhalation** - Breathing in (air enters lungs)

**Exhalation** - Breathing out (air leaves lungs)

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IMPORTANT FACTS FROM CHAPTER

1. **Saliva breaks starch into sugar** - This is why rice tastes sweet when chewed long

2. **Small intestine is 6 meters long** - Much longer than large intestine

3. **Villi increase absorption surface area** - Thousands of projections help nutrients enter blood

4. **Ruminants chew 8 hours daily** - To properly digest tough plant material

5. **Birds have gizzards, not teeth** - Gizzard grinds food with help of swallowed stones

6. **We breathe without thinking** - Breathing is automatic, controlled by diaphragm

7. **Nose filters air** - Tiny hairs and mucus trap dust

8. **Alveoli are tiny sacs** - Where oxygen enters and carbon dioxide exits blood

9. **Exhaled air has more CO2** - Proven by lime water turning cloudy

10. **Gut bacteria are helpful** - They produce essential nutrients and keep digestion healthy

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HEALTH AND WELLNESS TIPS

**For Better Digestion:**

Chew food properly (at least 20-30 times)

Eat at proper meal times

Practice mindful eating (focus on food)

Avoid overeating

Brush teeth twice daily

Rinse mouth after each meal

Eat fiber-rich foods (fruits, vegetables, whole grains)

Include fermented foods (curd, buttermilk, pickles, kanji)

Use digestive spices (ginger, black pepper, cumin) as mentioned in ancient Charaka Samhita

**For Better Breathing:**

Breathe through nose, not mouth

Practice deep breathing exercises

Stay in clean, dust-free environments

Avoid smoking and pollution

Exercise regularly to strengthen lungs

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QUICK ANSWER GUIDE FOR COMMON QUESTIONS

**Q: Why does starchy food taste sweet when chewed long?**

A: Because saliva contains an enzyme that breaks down starch into simple sugars.

**Q: Why are we called "small intestine" even though it's 6 meters long?**

A: Because it is narrow in diameter. The large intestine is shorter (1.5 m) but wider.

**Q: How can we survive longer without food than without air?**

A: Because respiration provides immediate energy. Without oxygen, cells cannot produce energy needed for survival.

**Q: Why do cows keep chewing when not eating?**

A: They are ruminants. They bring partially digested food back to mouth to chew again (rumination) for better digestion.

**Q: How do birds digest food without teeth?**

A: They have a gizzard (muscular chamber) that grinds food. They also swallow stones (grit) to help grinding.

**Q: What is the difference between breathing and respiration?**

A: Breathing = physical process of moving air in and out. Respiration = chemical process of releasing energy from nutrients in cells.

**Q: What does lime water turning cloudy prove?**

A: That exhaled air contains more carbon dioxide than inhaled air (CO2 reacts with lime water to make it cloudy).

**Q: Why should we breathe through the nose?**

A: Nose hairs and mucus filter dust and dirt, making air cleaner for lungs.

**Q: What do villi do in the small intestine?**

A: They increase surface area for absorption of nutrients into the blood.

**Q: What happens if someone has celiac disease?**

A: Their body cannot digest gluten. It damages the small intestine lining, preventing nutrient absorption. Solution: Avoid wheat, eat gluten-free millets.