Everything you need to know about science

Plant and animal systems:

Plant system:

- A plant system is made up of different parts of plants working together. Each

Plant part has its own function:

Flowering plant system:

1. Leaves 2. Roots3. Stems4. Flowers5. Fruit6. seeds

Leaves: Leaves grow out from stem Main function is to make food during PHOTOSYNTHESIS. Usually are flat, broad and green - it allows them to absorb more

sunlight and produce more food. Have openings to let out waste substances (Stomata) produced during

food production.

Leaf Structure: It is made up of layers of different types of cells.

Stomata: Tiny opening found mostly underside of the leaf Singular is Stoma Controls the water movement and Exchange of the gases in the leaf Transpiration -- is the process of losing water through the open Stomata

in the leaf.

Cuticle:

It is a protective layer on the outer surface of the cells. It prevents dehydration (Losing too much water).

Leaf Stalk:

A thin structure that joins main body of leaf to the stem. Each leaf has a leaf stalk

Veins:

A leaf has veins Central Vein called MIDRIB It is an Extension of the leaf stalk Midrib branches off into numerous smaller veins. Altogether they form a Vein system - called VENATION or Vein pattern There are two types of Leaf vein patterns

o Net - Spreads out within a leafo Parallel - Runs parallel to the edge of the leaf

Photosynthesis: It is the process of using carbon dioxide and water in the presence of light to make food in green plants. It takes place in the two or three layers of cells found on the upper surface of leaf.Photo ---- > LightSynthesis ---> to make

Carbon dioxide and water are converted into sugar and oxygen. Plants are able to make food because their leaves contain a green

pigment called Chlorophyll which can trap light.

Carbon dioxide + water Sugar + Oxygen

Leaf Shapes, edges and surface characteristics:

Chlorophyll

Sunlight

Simple - Made up of a single leaf blade. Ex - Papaya, Balsam and frangipani.

Compound - Made up of small leaf blades called "Leaflets". Leaflets grow from one central leaf stalk. Ex- Flame of the forest, Angsana and rubber trees.

Leaf Edges:

Entire-Edge - Where there is no indentation of any kind on the leaf. Jagged-Edge - There are tiny jagged teeth around the edges of the leaf Lobed - Edge - There are sections along the edge of the leaf.

Leaf Surface:

Smooth Waxy surface - These will not lose water easily Hairy surface

Roots:

• Roots usually grow downwards into the ground• The main function is to absorb minerals and water• Also anchor the plant into soil and hold it firmly to the ground• Root has

o Root hairs - small hair like extensions from the rooto absorb minerals and watero these increases the surface area of the root and enable the root to absorb

more water (water is used in photosynthesis to make food, minerals are important for the proper growth of the plant)

• Types of roots 1. Tap roots2. Storage roots3. Fibrous roots4. Aerial roots5. Prop roots6. Clasping roots

Tap roots -

Main roots or the primary roots largest structures Many smaller roots that grow out of main root. Smaller roots are called secondary or lateral roots Vegetables like - carrots & radish have tap roots

Storage root:

• These store food

• These are swollen

• Carrot is a tap root as well as storage root• Ex- Radish, turnip, tapioca

Fibrous Roots:

• These are equal in size and each produces smaller lateral roots

• There is no main root

• These do not grow deep into the ground but spread horizontally.

• Plants such as - grass and many shrubs are example.

Aerial Roots:

• These grow above ground• Also called breathing roots• These can absorb moisture from air• The mangrove tree has roots that stick out of the swampy grounds

Prop Roots:

• These grow outwards from the stem and hang in the air• They reach out for the ground and grow into the ground to provide

additional support to the plant• Heavy plants like banyan tree have prop roots•

Clasping Roots:

• Plants with weak stems sometimes have roots that grow from the stem and cling on to supports, so that they get enough light for photosynthesis.

• Money plant & orchid

STEM:

• Is the main trunk of a plant with buds and shoots developing.• Provides structure and support for the leaves, flowers and fruit.• Carries nutrients and water to various parts of the plant.• In some plants, the stems store food.• Generally upright and above the ground, there are some stems that

grow underground or creep along the ground.• E.g.: Corms, Bulbs, Rhizomes, Runners, tubers, Climbers.• Easily recognized as they contain buds and sometimes leaves.• Outer covering of stem is known as the epidermis or bark.• Epidermis –It is a single layer of covering found on herbaceous stems

whereas the bark is a multi-layered woody covering found on woody stems.

INSIDE A STEM

• A major function of the stem is to transport water, nutrients and food through the plant.

• The internal tubes in the stems act like the water pipes in a house or the blood vessels in a body. This system is called the vascular system.

• The tube that transports food is called the phloem.• The tube that transports water and minerals is called the xylem.

Cambium:

• It is the growth tissue of the plant• Two Types

o Vascular o Cork

• Cambium in buds produces tissue that increases the length of the stem.

• Cork cambium covering the stem increases the thickness.• For some plant, any injury to the cambium layer can kill the entire

plant.

Xylem - It transports water and minerals from the roots to the other parts of the plant such as the stem and the leaves

Phloem - It transports food that is made in the leaves to other parts of the plant. They transport the food upwards to the flowers and fruit and downwards to the roots.

•

Stem Variations:

• E.g. - Potatoes and asparagus• These stems are swollen as they store food• Animals and humans eat them as food• The roots are sometimes called - as they grow in the soil• There are usually new shoots or buds growing on it.

Other forms of variation like Tubers and Bulbs are sold in dormant form for planting later.

• E.g. - Dahlia tubers and tulip bulbs

Rhizomes are the underground stems that spread itself horizontally.

• It is also swollen as it stores food.• It is also edible• E.g. are - ginger and turmeric• Shrubs and trees have woody stems that enable the plant to stand

upright to reach out for more sunlight.

For Ex - Trees can be killed if the cambium layer, located just inside the bark is damaged.The vascular cambium is found between the phloem and xylem

Creepers or climbers:• Creepers have weak stems, e.g. - sweet potato, strawberry, carpet

grass and mimosa will creep along the ground.• Climbers will climb on to supports using their modified plant parts

Flowers, Fruits and seeds:

• A morning glory plant twines around a support, a grapevine climbs on to supports using tendrils and a money plant has clasping roots to hold on to supports.

Flowers:

• Flowers are the seed producing parts of a plant• Function of flower is for plant reproduction (this ensures continuity of

their own kind)

• Pistil is the female part of the flowero It includes - Stigma - the surface that captures and holds pollen

grainso The Style - the connection between the stigma and the ovary.

• Stamen is the male part of the flowero It includes - Filament - which holds the Anther.o Anther - is where the pollen grains are formed and held until

released.• A flower that has both male and female parts is called Complete or

Bisexual.• The flowers that have only male or only female parts are called

Incomplete or Imperfect or asexual.• The other parts of flower are Sepals and Petals

o Sepals - They are usually green in colour. Protect the bud of a young flower.

o Petals - These are brightly coloured so as to attract insects such as

butterflies and birds to pollinate them.

• Flowers may also contains sweet aromatic Substances such as nectar to attract insects and

Birds for pollination.• After pollination, the ovules in the ovary are

fertilised and a fruit is formed.• The ovary of the flower develops into a fruit and

the ovules develop into the seed of the fruits.• The fruit protects the seeds and helps to disperse the seeds far away from

the parent plant.

Fertilisation:

• Fertilisation is the process that happens after pollination• In this process the pollen grains fuses with the ovule to form a fertilised egg.• After fertilisation, part of the flower dry up and fall off.• These parts are the sepals, petals, stamens and top parts of the pistil• The base of the pistil, the ovary, grows and swells and develops into a fruit.• The seeds develop from the ovules (containing fertilised egg cells) which are

located in the developing fruit.

Functions of the parts of a seed:

• The seed in a fruit contains three main partso seed coat - protects the embryo until conditions are favourable for

germinationo endosperm (stored food) - will nourish the embryo as it develops

into a seedling and is large enough to make its own food by photosynthesis

o Embryo

Seed Germination:

• Germination happens when conditions are favourable i.e. warmth, water and air (oxygen)

• Some seeds are also able to germinate even after exposed to extreme conditions - freezing or passing through digestive system that breaks down the seed coat

• Germination stimulates the plant embryo to begin cell division. • The embryo first develops the first root (radicle). Then the cotyledons -

often called seed leaves emerge.

• As the seedling does not have green leaves - it gets its food from seed leaf.• The seed leaf does not make its own food, rather uses its supply of stored

food.• After the stored food in the seed leaf is used up, it withers.• Then the first true leaves appear and the young plant is ready to make its

own food through photosynthesis.

Functions of the Fruits:

• Store food made by leaves• Protect the seeds• Help to disperse the seeds for growth into plant• Succulent Fruits: Fruits that have Tasty, thick and fleshy layers.

o Succulent fruits are usually dispersed by animals by attracting the animals to eat them.

o Succulent fruits have either too big seeds - which are hard to eat, or small seeds that cannot be digested and will be passed out as waste from animals’ digestive system.

Human Systems:

• A system is a group of organs that work together to perform a particular function/job.

• It is also the final part of the progression from cells to tissues to organs to systems.

• Cells Tissues Organs Systems• A system rarely works alone• A system works with other systems to allow body to maintain a stable

internal environment conducive for survival• Organs are part of a system• All systems in an organism are interconnected

Example of systems working together in our body

Organs

• Perform specific functions • For e.g. - sense organs like nose (smell), eyes (see), ears (hear), tongue

(taste) and skin (touch).• Organs take in information and send to brain for processing.• Each sense organ collects information about the world and detects

changes in the surrounding.

• All senses depend on the working Nervous system.

• Our sense organs start to work when something stimulates the special nerve cells called receptors in a sense organ.

• Once stimulated, the receptors send nerve impulses along sensory nerves to the brain.

• The brain then tells what the stimulus is.

• How do we see?o Eyes are made up of lenses, retina and nerves.o Light enters through the lens.o Lens focuses the light onto a point on the retina (found at the back of

the eye).o The nerves attached to the retina will send messages to the brain

about the images seen by the eye.

Digestive system

• Digestion is the process of breaking down food into smaller pieces.• It involves the mixing of food, its movement through the digestive tract and

the chemical break down of the large molecules into smaller molecules.

• Why is digestion important?

The food (bread, meat, vegetables) we eat is not in a form that the body can use as nourishment; therefore digestion is the process by which food is broken down into smaller molecules of nutrients for absorption by blood.

• Movement of food through the systemo Mouth-

Saliva – It makes the food mushy, easy to swallow. Moistens the food so it slides down the throat. It also breaks down starch into simple sugars.

Tongue – it helps to push the food around while chewing with the teeth and when ready to swallow it pushes the mushed-up food called – bolus, towards the back of your throat (into the oesophagus/gullet).

Teeth – It helps to grind / chew the big pieces of food into smaller parts.

o Oesophagus (Gullet) – Stretchy pipe about 25 cm long. Moves food from back of throat to stomach When mushed up food is swallowed, a special flap called

“epiglottis” flops down over the opening of the wind pipe to ensure the food enters oesophagus only.

Muscles in the oesophagus moves in a wave like manner to slowly squeeze the food through the pipe, it takes 2 to 3 sec.

o Stomach – Stretchy sack attached to the end of the Oesophagus. Three important functions

It stores the swallowed food and liquid It breaks down the food into liquid mixture It empties the liquid mixture into the small intestine.

Stomach is like a mixer, churning and mashing together the small balls of food that came down the gullet into smaller pieces.

It does this with the help of strong muscles in the walls of stomach and gastric juices that come from stomach walls.

In addition to breaking food, gastric juice also helps to kill bacteria that might be in the eaten food.

o Small Intestine – Long tube (around 7 m long) with 3.5 to 5 cm diameter. It breaks down the food mixture further so that the body can

absorb all vitamins, minerals, proteins, carbohydrates and fats. The food is digested in the small intestine and dissolved in the

juices from pancreas, liver and gall bladder. These juices help to digest food and allow the body to absorb

the nutrients. Pancreas –

Juices from pancreas help the body to digest fats and protein.

Liver – The juice called BILE helps to absorb fats into blood stream

Gall Bladder – Serves as a storehouse for Bile, storing it until the body needs it.

Food spends 4 hrs in small intestine and will turn into watery thin mixture.

Finally, the nutrients from the food will be passed into the blood.

The waste products of this process include undigested parts called – Fibre is moved into the large intestine.

o Large Intestine – Last stop in digestive system, 7 to 10cm in diameter, 1.5mt in

length and is fatter than small intestine. Appendix – part of digestive tract but serves no purpose. After nutrients are removed, the left over waste has to be

passed out of the body. Before waste leaves the body, it passes through the colon. Colon –

Part of large intestine Here the water and some left over minerals are

absorbed into the blood streams After water is removed, the waste gets harder as it moves

along and is called – stool / Faeces. The large intestine pushes the stool into the rectum, the very

last stop of the digestive tract, from where it is pushed out through Anus.

MUSCULAR SYSTEM• 600 muscles in human body.• Helps us to do almost everything, like-walking, running, pumping blood

through the body. • Muscles are made up of a type of elastic tissue that allows them to

expand or contract.• 3 types of muscles-

o Smooth –also called involuntary muscles. You cannot control these types of muscles. Your brain and body control these muscles without you even thinking about them. EX-bladder, stomach.

o Cardiac – like smooth muscles, cardiac muscles work by themselves without our control. Heart is made up of cardiac muscles.

o Skeletal –these are voluntary muscles. You can control what they do. These make up the musculoskeletal system – combination of muscles and

skeleton/bones. They work together to give the body the strength and the ability to move.

• In most cases, skeletal muscle is attached to one end of a bone. It stretches all the way across a joint and then attaches again to another bone.

•• Skeletal muscles are held to the bone with tendons.• Tendons are cords made of tough tissues; they work as special

connectors between bone and muscles.

Muscles work in pairs

• Muscles cannot push but can only pull. So they often work in pairs.• You need another muscle to pull them back to their original position.• For e.g. –bending your arm at the elbow requires both the biceps and

the triceps muscles in your arms.

•

Major Skeletal muscles found in human body

Muscle Where it is found UsesDeltoid Shoulders Help to move shoulders

such as swinging a softball bat and shrugging shoulders

Pectoralis (pecs) Each side of upper chest When boys reach puberty, their pectoral muscles become larger. Many athletes and body builders have large pecs too.

Rectus abdominus (abdominals)

Below the pectorals, down under the rib cage.

Responsible for flexing lumbar spine during sit –ups.

Quadriceps (quads) On the front of your thighs

Many people who run, bike or play sports develop large, strong quad.

Gluteus maximus Under the skin and fat on your buttocks.

It is involved in jumping and going upstairs.

Skeletal system

• Protect delicate organs and provides support.• Skeletal system work closely with the muscular system to help you

move.• Bone creates a framework to which muscles and organs can connect. • Skull protects brain; ribs protect internal organs from impact.• Skeletal system is made up of bones, ligaments and tendons.• Ligaments- connect bones to bones and tendons- connect bones to

muscles.• Most bones are hollow and contain marrow cells.• The marrow tissues in the cavity of the bones produce red blood cells

and white blood cells.

• Bones are hollow making them strong and light.• It is in the centre of many bones that bone marrows make new RBC and

WBC.• RBC – ensures oxygen is distributed to all parts of body• WBC – ensures that body is able to fight germs and diseases.

What is Bone Marrow?

• It is a special, spongy, fatty tissue that houses stem cells. • These stem cells change into RBC and WBC and platelets.• Platelets help to clot blood to stop bleeding if there is open wound.• Only skull, sternum, ribs, pelvis and femur bone contain bone marrow.•

Axial Skeleton and Appendicular Skeleton

• Skeleton is divided into Axial and Appendicular• Appendicular –

o Consists of arm bone, leg bone and girdles.o Girdles are collection of bones that connects limbs to the rest of

the skeleton

• Axial –

o Consists of skull, back bone (vertebrae), ribs and breast bone (sternum).

Bone FunctionsSkull Give shape to the head

Protects the brainBackbone (vertebrae) Connects the skull to the pelvis

Protects the spinal cordSupports the skullKeeps the body upright

Ribcage Protects the heart and lungsPelvic (Hip) Supports the body mass

Protects organs in the lower abdomen

Joints:

• Places where bones meet• Most joints are movable while few are fixed like those between the

bones in your skull• The human body has around 100 joints. Lubricated with an oily liquid

called synovial fluid so that they can bend and move freely without friction.

• Three main types of joints

o Movable jointso Ball and socket joints – allows freedom of movement in several

directions, it can be found at the shoulder joint o Hinge and pivot joints –

Hinge joint Allows movement in single plane. E.g. joint in your

knee. Pivot joint

The degree of freedom of movement allowed by a pivot joint lies somewhat between that of ball and socket and hinge joints. E.g. joint in your wrist, ankles and between the top two vertebrae.

o Smooth and slippery cartilage covers the ends of the bones to reduce friction during movements.

Circulatory Systems• It is the transportation system of the body• It carries substance like nutrients, oxygen, water to all parts of the body• It also carries waste products created by body, out of it.• The system is connected to all the cells of the body so that it can

transport oxygen efficiently• During breathing – the circulatory system carries oxygen to your cells

and carries dissolved carbon dioxide back to the lungs• The main components are heart, blood and blood vessels• The heart is the pump – a muscular organ. Unlike other muscles, it never

gets tired.• The heart is divided into four chambers• As blood is pumped from the heart, it passes through a system of

arteries, arterioles and capillaries.

• Capillaries – o These vessels allow most of the transfer of substances and dissolved

gases.o They are very small and have thin walls to allow easier passage of

compounds including nutrients, glucose, carbon dioxide and waste products.

• After the capillaries, blood passes through venules and veins. The veins lead the blood back to the heart.

• Blood carries substances around the body• It helps to fight germs, heal wounds and control body temperature.• Blood is made up of RBC and WBC and platelets in pale yellow liquid called

plasma.• Blood vessels:

o Tubes in the body to carry blood. Three types – arteries, veins, capillaries

o Arteries – Strong blood vessels that carry blood from heart to other parts of the body

o Veins – that carries blood back to the heart from various parts of the body

o Capillaries – are the smallest blood vessels – only one cell thick so that oxygen and other substances needed by the body can pass through easily.

• Arterioles :o When artery branches into smaller and smaller arteries, until it is

hard to see. Those are called arteriole or microscopic arterieso The arterioles continue to branch into tiniest blood vessels which are

capillaries• Venules :

o Capillaries fuse into larger vessels, the venules. These continue to fuse together into larger and larger vessels, until they eventually form the veins.

•

Blood circulation:

• Blood passes through heart twice during one complete circulation of the body

• First, blood is pumped from the right side of the heart to the lungs.• At the lungs, blood picks up fresh oxygen which has been breathed in.• This blood then returns to the left side of the heart.• The oxygen rich blood is then pumped to the rest of the body to deliver

oxygen.• The level of oxygen becomes low – this deoxygenated blood returns to

the heart to begin the whole cycle again.

Respiratory Systems

• It is made up of nose, mouth, a tube called pharynx (throat), another tube called the trachea (wind pipe), and the lungs

• There are two lungs where the exchange of gases between circulatory and respiratory systems takes place.

• The purpose of respiratory system is to bring oxygen into the body and get rid of the carbon dioxide produced by the body

• The human respiratory system also interacts with the digestive system – mouth and pharynx are both used for swallow and breath.

• The branching point – the epiglottis directs the food to stomach and air to lungs

• Respiratory system is connected to the nervous system in your nose where smelling takes place

• Alveoli – These are rich in blood vessels. If the walls of the alveoli of both lungs is opened and spread out, it will cover a surface area of 56 to 93 meter square ( a 4 – room HDB flat)