Symptoms

Chest pain that may feel like pressure, tightness, pain, squeezing or aching.

Pain or discomfort that spreads to the shoulder, arm, back, neck, jaw, teeth or sometimes the upper belly.

Cold sweat.

Fatigue.

Heartburn or indigestion.

1. Variation (Darwin’s Core Discovery)

Darwin observed that no two individuals of the same species are exactly alike.

• Variations can be:

  • Size

  • Shape

  • Color

1. Selective Breeding (Artificial Selection)

Selective breeding, also called artificial selection, is the process where humans deliberately choose organisms with desirable characteristics and breed them together so that those characteristics become more common in future generations.

This process works because:

• Individuals in a species show variation

• Many traits are genetic and can be passed on

• Choosing specific parents increases the chance that offspring will inherit those traits

1. Inheritance

Inheritance is the process by which traits (characteristics) are passed from parents to their offspring.

What are traits?

Traits are features such as:

• Eye color

• Hair color

1. KEYS IN BIOLOGY

What are Keys?

In biology, keys are scientific tools used to identify unknown organisms such as animals, plants, or microorganisms by studying and comparing their observable characteristics.

A key helps us decide what an organism is and to which group it belongs by following a fixed and logical sequence of steps.

Why are Keys Needed?

The living world contains millions of organisms, many of which look similar. It is not possible to identify organisms by guessing. Therefore, keys are needed because they:

Protecting the Environment

• Protecting the environment means conserving natural resources and preventing damage to ecosystems

• It involves protecting air, water, soil, forests, wildlife, and climate

• Human activities like pollution and deforestation seriously harm the environment

• Environmental protection helps maintain ecological balance

• It ensures sustainable use of resources for future generations

HABITAT DESTRUCTION

🔹 What is a Habitat?

A habitat is the natural home of plants, animals, and microorganisms where they get:

• Food

• Water

• Shelter

Pollution

Historical background (quick)

• Pollution increased rapidly after the Industrial Revolution

• Earlier: natural balance absorbed waste

• Now: human activities exceed nature’s ability to recover

  What pollution does to humans

  
  

POPULATION

Population growth happens in patterns:

Types of Population Growth

1. Exponential growth

2. Happens when food is unlimited

3. Population increases very fast

DECOMPOSERS

What are decomposers?

Decomposers are organisms that feed on dead and decaying plants, animals, and organic waste and break them down into simpler substances. These substances are returned to the environment and reused by plants.

They are also called nature’s recyclers.

3. Position of Decomposers in an Ecosystem

An ecosystem has:

Food Webs — Detailed Understanding

A food web is a complex system of overlapping food chains that shows how organisms are linked by feeding relationships.

Why food webs are important

• Increase ecosystem stability: if one food source disappears, organisms may switch to another.

• Show real-life feeding behavior (animals don’t eat just one thing).

• Help scientists predict the impact of changes like pollution, deforestation, or species extinction.

What ecology focuses on

• Organisms – plants, animals, microbes

• Environment – air, water, soil, climate

• Interactions – who eats whom, competition, cooperation, and adaptation

Levels of ecological study

• Individual – how a single organism survives

1. Adaptations Based on Habitat

Desert Animals

• Camel

  • Long eyelashes keep sand out

  • Broad feet prevent sinking in sand

  • Can survive many days without water

Flowers

Flowers are the reproductive organs of flowering plants. Their main role is to make reproduction possible.A typical flower has four main parts:

• Sepals – protect the flower when it is a bud

• Petals – usually colorful and scented to attract pollinators

• Stamens (male part) – produce pollen grains

• Pistil/Carpel (female part) – contains the ovary with ovules

PLANTS

Plants are autotrophs, meaning they make their own food using sunlight, water, and carbon dioxide.

Main Parts of a Plant

• Roots – absorb water & minerals, anchor plant

• Stem – transports water, minerals, food

• Leaves – photosynthesis

What “keys” are in biology

In biology, a key—especially a taxonomic or identification key—is a tool used to figure out what an unknown organism is. It works by asking a series of questions about the organism’s traits so you can narrow down the possibilities until you reach the correct species, genus, or group.

The most common kind is the dichotomous key, which gives you two opposite choices at each step.

How keys work

1. Start with broad traits The key begins with a very general difference—like “wings vs. no wings,” “leaf simple vs. leaf compound,” or “lives in water vs. lives on land.”

2. Choose the matching statement You observe the organism and decide which description fits it.

Charles Darwin

1. Who Was Charles Darwin?

Charles Darwin (1809–1882) was an English naturalist and biologist best known for developing the theory of evolution by natural selection. His work transformed modern biology and explained how species change over long periods of time.

2. Darwin’s Journey: How It All Started

The HMS Beagle Voyage (1831–1836)

Darwin traveled around the world on a scientific expedition aboard the ship HMS Beagle.This journey provided him with the observations that led to his theory of evolution.

Natural Selection in Action

Natural selection is a key mechanism of evolution. It describes how certain traits become more or less common in a population depending on how they affect survival and reproduction.

But “natural selection in action” means actually observing this process happening in real time, in real organisms, often across just a few generations.

How natural selection works

1. Variation Individuals within a species are not identical. Some bacteria, for example, might have a slight mutation that changes how they grow.

2. Environmental pressure Something in the environment challenges survival — predators, diseases, climate, antibiotics, lack of food, etc.

Natural Selection in Biology

Natural selection is a fundamental mechanism of evolution that explains how species change over time. It focuses on how certain traits become more common because they help organisms survive and reproduce.

1. Overview of Natural Selection

Key Points

• It is a non-random process.

• Acts on existing variations within a population.

1. What Is Selective Breeding?

Selective breeding is a process where humans intentionally choose which animals or plants should reproduce, based on traits that are useful or desirable.

Key Features

• Humans pick the parents instead of letting nature choose.

• Offspring inherit traits from these selected parents.

• Over many generations, populations become more specialized.

Inheritance in Biology

Inheritance in biology refers to the process by which traits or characteristics are passed from parents to their offspring. These traits include physical features, internal functions, and even certain behaviors. The basis of inheritance is DNA, which carries the instructions for building and operating living organisms.

Genes

A gene is a segment of DNA that contains the instructions for making a specific protein. Proteins carry out most of the functions in a cell and influence the traits that an organism shows.

Important points about genes:

1. Humans have more than twenty thousand genes.

Inheritance in Biology

Inheritance is the process by which traits are passed from parents to offspring through genes. These genes are segments of DNA located on chromosomes, and they contain instructions for building proteins that shape an organism’s characteristics.

Key points:

• Genes come in pairs — one from each parent.

• Different versions of a gene are called alleles.

• Some alleles are dominant (expressed even if only one copy is present), while others are recessive (expressed only when two copies are present).

What Is Variation?

• Variation refers to the differences that occur among individuals of the same species.

• These differences may be in physical appearance, behavior, or genetic makeup.

• Because of variation, no two individuals are exactly alike.

• This diversity is essential for the survival and evolution of species.

Variation ensures that:

1. Key Words (Easy Definitions)

Environment: everything around living things (air, water, soil, plants, animals).Ecosystem: a place where living things and non-living things interact. Biodiversity: many different kinds of plants and animals living together. Habitat: the home of a plant or animal. Conservation: protecting nature so it is safe for the future. Pollution: harmful things put into air, water, or land. Sustainable: using resources without wasting them. Eutrophication: too much fertilizer enters water, algae grow too much, and fish die. Biomagnification: harmful chemicals become stronger as they move up the food chain. Greenhouse gases: gases that warm Earth (like carbon dioxide).

2. How Humans Harm the Environment

Pollution

• Water pollution: dirty water from farms and factories enters rivers and oceans.

• Air pollution: smoke from cars and factories.

Habitat Destruction

What It Is

Habitat destruction occurs when natural environments are altered so extensively that the species living there can no longer survive. It is one of the major drivers of biodiversity loss worldwide.

Main Types of Habitat Destruction

1. Deforestation

• Removal of large forest areas for agriculture, logging, mining, or urban development.

Pollution in Biology — Full, Easy-to-Understand Overview

Pollution in biology refers to how harmful substances introduced into the environment affect living organisms—plants, animals, microbes, ecosystems, and even human health. It’s a major chapter in ecology and environmental science.

1. What Is Pollution?

Pollution is the introduction of contaminants into the environment that cause harm or life-disrupting effects. These contaminants can be:

• Chemical (pesticides, metals, industrial chemicals)

• Physical (plastic waste, heat)

What is Population in Biology

A population is a group of individuals of the same species that live in the same geographical area at the same time and are capable of interbreeding.

Example: All deer in a particular forest form a population.

Key Characteristics of a Population

1. Population Size (N)

The total number of individuals in the population.

What Are Decomposers

Decomposers are organisms that break down dead plants, dead animals, and waste materials. By doing this, they recycle nutrients back into the environment so other living things can use them.

They are essential for keeping ecosystems healthy because without decomposers, dead matter would pile up and nutrients would eventually run out.

Main Types of Decomposers

1. Bacteria

1. FOOD WEBS

1.1 What a Food Web Is

A food web is a big network showing who eats whom in an ecosystem. It connects multiple food chains together so you can see how every plant and animal depends on others.

• Shows complex connections between organisms

• Explains how energy and nutrients move

• Helps us understand how nature stays balanced

1. Levels of Ecology

1. Organism

   • One single living thing, like a bird, tree, or bug

   • How it survives and fits in its environment

2. Population

   • A group of the same kind of organism living together

Animal Adaptations

1. Structural (Physical) Adaptations

Changes in the body structure to survive.

1. Camouflage – helps hide from predators.

   • Chameleon: changes color to blend with surroundings.

   • Leaf insect: looks like a leaf.

1. Plant Adaptations

Plant adaptations are special features that help plants survive in their environments. These features make it easier for plants to get sunlight, water, air, protection, and grow better.

1.1 Structural Adaptations

• Thick waxy layers help plants keep water inside.

• Spines protect plants from animals and reduce water loss.

• Long roots help plants reach water deep underground.

Dispersal

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Seeds contain embryo plants. When they start to grow, each plant need water, light and mineral salts in order to grow well.

If all the seeds just fell of the plant onto the ground, they would all be trying too grow in the same place. The new little plants would all compete with each other for water, light and mineral salts. They would also have to compete with the parent plant, too.

The new plants have a better chance of growing if they are in a different place. They need to be dispersed away from the parent plant and others

if seedlings (young plants) grow next to there parent plant they may not get enough water, light or mineral salts to grow well.

Mineral salts are inorganic nutrients absorbed by plants in the form of dissolved ions from the soil solution. These essential elements, which include both macronutrients and micronutrients, are vital for a plant's growth.

Plants absorb mineral salts as ions from the soil solution primarily through their roots.

ineral salts are essential for plant growth, providing necessary elements like nitrogen, phosphorus, and potassium, which support cell structure, photosynthesis, and enzyme activity.

Magnesium and nitrate are key components of the essential inorganic salt, magnesium nitrate.

Difference between Fertilizer and Manure Mineral salt fertilizers are inorganic compounds that provide essential nutrients like nitrogen, phosphorus, and potassium to plants in a readily available form.

Summary

Energy Transfer

Photosynthesis reaction needs a supply of energy to make it happen. This energy comes from light. During photosynthesis, the plant's leaves absorb the energy of light. The energy is stored in the glucose that is made. The glucose is a store of chemical potential energy.

Storing Carbohydrates

Glucose is a sugar. Sugar belong to a group of chemicals called carbohydrates.

Plants usually make much more glucose than they need to use immediately. They store some of it as glucose. Glucose is a soluble in water, which makes it difficult to store inside a cell.

 Defense System 🧬

The immune system is your body’s personal army. Its main job? Protect you from invaders like bacteria, viruses, fungi, and parasites. It spots anything that doesn’t belong (like germs) and destroys it before it causes trouble. Think of it as a high-tech security system that’s always on patrol — scanning for intruders and neutralizing them fast.

Two Main Parts 🧠

Your immune system has two big branches:

• Innate Immunity: Fast, non-specific, always ready to act.

• Adaptive Immunity: Slower at first but learns and remembers enemies for the future.

Definition

Enzymes are biological catalysts. They speed up chemical reactions inside living organisms without being used up. For example, digestive enzymes like amylase help break down starch into sugar quickly, which would otherwise take too long.

Function

The main function of enzymes is to lower the activation energy of reactions. This means reactions can happen faster and at normal body temperature, instead of needing extreme heat or energy. That’s why life processes can occur smoothly in cells.

Active Site

Every enzyme has an active site, a special region where the substrate (the molecule it acts on) binds. The active site’s shape matches only its specific substrate, like a lock fitting a key, which is why enzymes are highly specific.

1. Only 2 research topic.

2. No mention of Santhosh Ji's work

3. Atomic research and respiration is not a specific topics

 It’s the process by which cells break down glucose (sugar) to release energy. This energy is used for all the activities in the body, like moving, growing, repairing tissues, and keeping warm.

There are two main types:

• Aerobic respiration: Needs oxygen.

• Anaerobic respiration: Happens without oxygen.

Aerobic Respiration – This is the main way our body gets energy. Glucose reacts with oxygen to produce carbon dioxide, water, and lots of energy (ATP). It mostly happens in the mitochondria of the cell.\

Mitochondria – These are called the “powerhouses of the cell” because most of the energy from aerobic respiration is produced here. They’re like tiny factories turning glucose into usable energy.

1. Cell Wall

• What it is: A strong outer layer.

• What it does: Protects the cell and gives it shape.

2. Cell Membrane (Plasma Membrane)

• What it is: A thin layer just inside the cell wall.

• What it does: Controls what goes in and out of the cell (like food, water, and waste).

The oesophagus is a muscular tube that connects the throat (pharynx) to the stomach. It plays a key role in the digestive system by transporting food, liquids, and saliva after swallowing.

How It Works

When you swallow, the food or liquid enters the oesophagus. The walls of the esophagus are lined with muscles that contract in a wave-like motion. This movement is called peristalsis, and it helps push the food down toward the stomach.

At the lower end of the oesophagus is a ring-like muscle called the lower oesophageal sphincter (LES). This muscle opens to let food into the stomach and then closes to prevent stomach contents—especially acid—from flowing back up. If this muscle doesn't close properly, it can lead to acid reflux or heartburn.

Structure and Location

The tongue is a strong, flexible, and muscular organ located in the mouth. It plays a key role in everyday actions such as eating, speaking, and interacting with our environment. Covered with a moist mucous membrane, the surface of the tongue contains many tiny bumps called papillae, some of which house the taste buds. These taste buds detect different tastes like sweet, salty, sour, bitter, and umami, allowing us to enjoy a wide variety of flavors.

The tongue is made up of several groups of muscles that work together to allow precise and varied movements. It can change shape, stretch, curl, and move in different directions with great control. This is what makes it so important for helping to position food during chewing, as well as shaping sounds during speech.

The upper surface of the tongue (the dorsum) has a rough texture because of the papillae, while the underside is smoother…

The digestive system is a group of organs in your body that work together to break down the food you eat, absorb the nutrients, and remove the waste. This system allows your body to get energy and stay healthy. It starts at the mouth and ends at the anus.

1. Mouth (Oral Cavity)

Digestion begins in your mouth when you chew your food. Your mouth has different parts that start breaking the food down:

Teeth

Teeth cut and grind food into small pieces so it can be swallowed and digested easily. There are four main types of teeth:

• Helps your blood clot properly, which is important to stop bleeding when you're injured.

• Supports bone health by helping the body use calcium effectively.

• May help prevent calcium from building up in the arteries, which supports heart health.

Types:

• Vitamin K1 – Found mostly in green leafy vegetables. Mainly involved in blood clotting.

• Vitamin K2 – Found in fermented foods and animal products. Plays a role in bone and heart health.

1. Connects the throat (pharynx) to the stomach.

2. Acts as a food pipe for transporting swallowed food.

3. Moves food using peristalsis (muscle contractions).

4. About 25 cm long in adults.

5. Lined with mucus to help food slide down smoothly.

6. Has circular and longitudinal muscles to squeeze food down.

The heart is a muscular organ located in your chest, slightly to the left. Its main job is to pump blood throughout your body, keeping you alive and healthy.

What Does the Heart Do?

• It sends oxygen to your body.

• It brings food (nutrients) to your cells.

• It takes away waste, like carbon dioxide.

• It works all the time — even when you sleep!