air pollution happens when harmful gases dust or smoke mix with the air we breathe
water pollution happens when dirty or harmful substances mix into water bodies like rivers lakes and oceans
Land pollution happens when the ground is covered or filled with harmful waste
long ago people found all their food in the wild
they hunted and killed animals
they ate berries and seeds
they didnt kill all the animals
they didnt eat all the berries
they made sure their were some food in the future
the food we eat gives us energy
the energy in our food began with the sun
the sunlight goes in plants giving it energy
when a deer eats the plant it gets its energy
when a tiger eats the deer it gets its energy
energy passes from 1 thing to another
a place where an organism lives is called a habitat
each organism has adaptation
adaptation helps it live in a particular habitat
fish have gills to breath under water
giraffes have thin skin to live in the african savanna
cactus has water in their stems
protozoa only has 1 cell
the cell of protozoa has to do everything that the protozoa needs to live
animals and plants have many cells
different cells take on different tasks
every cell is specialized to do a particular function
red blood cells carry oxygen to the body
🦠 1. Protozoa – Single-Celled Organisms
Protozoa have only one cell.
The single cell of a protozoa performs all the functions needed for it to live — eating, moving, and reproducing.
Protozoa are so small that we can see them clearly only under a microscope.
Because they have just one cell, protozoa do not have tissues.
🧫 2. Multicellular Organisms – Plants and Animals
Plants and animals have many cells.
In multicellular organisms, different cells perform different tasks.
Each cell is specialized to do a particular function that helps the organism survive.
🔬 3. Specialized Cells and Their Functions
Here are some examples of specialized cells and their roles:
Red blood cells – carry oxygen to all parts of the body.
Nerve cells – transfer messages throughout the body.
Root hair cells – grow from the outer layer of the root and absorb water from the soil.
Plant root cells – help take in water and minerals from the soil to support the plant.
🧩 4. Tissues – Groups of Similar Cells
A tissue is a group of cells that perform the same function.
Example: Muscle tissue helps in movement.
The human body is made up of many different tissues.
Protozoa don’t have tissues because they are single-celled, but plants and animals do.
🫀 5. Organs – Groups of Tissues
Organs are formed when different tissues work together to perform a special job.
Example:
In humans, the heart pumps blood.
In plants, roots, stems, and leaves are organs that perform specific functions.
Each organ in animals or plants usually has several types of tissues.
all animals are made of cells
their are a lot of cells in animals
like plants animal cells have cell membrane cytoplasm and nucleus
animal cells dont have cell wall
nucleus controls the cell
protozoa are things that only have 1 cell
all living things are made of cells
cells cant be seen without microscope
you need microscope to see cells
plant cells are often larger then animal cells
plant cells have a nucleus
plant cells in sunlight often have chloroplast
most micro organisms are harmless
many of them are useful to us
some micro organisms can make us sick
diseases caused by micro organisms are called infectious diseases
one kind of bacterium causes a disease called tuberculosis
louis pasteur was the first person to discover that micro organisms can cause disease
muscles are organs that help us move
the muscles are attached to the bones
tendons are very strong
tendons dont stretch
muscles can get shorter
when the muscles contract they pull the radius and scapula
Their are 2 types of joints moveable and fixed joints.
The jaw bone is joint to the rest of the skull.
The skull has a fixed joint.
The shoulder joint can move in almost any direction.
The cranium is made of several firmly joint together.
The elbow joint is a hinge joint.
cell structure means how a cell is made
all living things are made of cells
you need a microscope to see cells
their are 2 main types of cells
their are 7 main parts of cells
the smallest cells are in bacteria
asexual reproduction means making a new living thing only using 1 parent
the baby looks exactly like the parent
if a plant grows another plant from it's stem without seeds it's asexual reproduction
in bacteria it happens in 1 celled things
in potato , onion or strawberry new plants grow from it's root , stem or leaf
asexual reproduction is fast and easy summary in potato onion or strawberry a plant can grow from it's leaf
Carbohydrates are nutrients found in food.
But our body can survive without them.
There are 3 types of carbohydrates, monosaccharides, disaccharides, and polysaccharides.
Monosaccharides - 1 sugar unit.
Disaccharides - 2 sugar units.
Polysaccharides - 3 or more sugar units.
Definition:
Enzymes are proteins that speed up chemical reactions in living organisms.
Function:
They help in digestion and other body processes by making reactions faster.
Examples:
1. Amylase – breaks starch into sugars.
Definition:Enzymes are helpers in our body that make chemical reactions happen faster.
1 Function:They help us digest food so our body can use it.
5 Easy Examples:
Amylase – breaks starch in bread, rice into sugar.
Protease – breaks protein in meat, egg into smaller parts.
Lipase – breaks fat in oil, butter into small pieces.
The skeletal system is all the bones in our body. It gives shape, helps us move, and protects organs.
Skull – protects brain
Ribs – protect heart and lungs
Spine – helps us stand
Nutrients are useful substances in food that our body needs for energy, growth, repair, protection, and proper functioning.
Carbohydrates – Main energy source, broken into glucose for fuel.
Proteins – Build and repair body tissues, make enzymes and hormones.
Fats – Store energy, keep the body warm, protect organs, help absorb vitamins.
They grow and develop.
Need food, water, and air.
Can reproduce.
Respond to changes around them.
🧍♀️ Humans and the Food Chain
🌿 What Is a Food Chain?
A food chain shows the flow of energy in an ecosystem — how energy passes from producers → consumers → decomposers.
Each level in a food chain is called a trophic level.
Example:🌾 Grass (Producer) → Grasshopper (Primary Consumer) → Frog (Secondary Consumer) → Snake (Tertiary Consumer) → Eagle (Top Predator)
🍽️ Where Do Humans Fit In?
Humans are omnivores — we eat both plants and animals.
Because of this, humans can appear at different trophic levels in different food chains.
Example 1: 🌾 Rice → Human → (Primary Consumer)
Example 2: 🌿 Grass → Goat → Human → (Secondary Consumer)
Example 3: 🐟 Algae → Small fish → Big fish → Human → (Tertiary Consumer)
⚡ Humans and Energy Flow
The energy in food that humans eat originally comes from the Sun.
Plants convert sunlight into chemical energy through photosynthesis.
When humans eat plants or animals, that stored energy is passed along the chain.
🌍 Human Impact on Food Chains
Humans greatly influence natural food chains through activities such as:
Deforestation: destroys habitats and reduces the number of producers.
Overfishing and hunting: disturb animal populations and can break food chains.
Pollution: chemicals in water and soil can enter the food chain (bioaccumulation).
Farming and pesticides: affect insects, birds, and soil organisms.
♻️ Food Webs and Interdependence
In real life, food chains connect to form food webs — complex networks showing how organisms depend on many others for food.
If one species is reduced or removed, it affects many connected chains.
Example: Fewer frogs → more insects → damaged crops → imbalance in ecosystem.
🌱 Role of Humans in Maintaining Balance
Humans can help protect the balance of food chains by:
Conserving forests and wildlife 🦜
Reducing pollution 🌊
Using sustainable farming and fishing methods 🚜
Recycling and reducing waste ♻️