science revision

Food and Nutrition

M - Movement     R - Respiration     S - Sensitivity     G - Growth     R - Reproduction     E - Excretion     N - Nutrition

Healthy diet

A healthy diet consists of Carbohydrate, gives body energy, Fat, gives body energy and can be stored, Protein, used for growth, Vitamins, help chemical reactions take place, Minerals, makes bones strong and help blood carry oxygen, Fibre, helps undigestive food pass through the gut, Water, dissolves chemichals so chemical reactions can take place.

• A healthy diet contains sufficient food to provide us with just the right amount of energy
• Energy in food is measured in calories or joules
• 1 calorie = 4.2 joules
• A young man needs about 2,500 kcal per day
• 2,500 kcal x 4.2 joules = 10,500 kj per day

Unbalenced diet

causes serious problems - obesity, eating excessive amounts - malnutrition - eating too little - Kwashiorkor - deficiency in protein - vitamins and minerals cause different illnesses depending on what vitamin or mineral you lack.

Photosynthesis

• The process by which green plants make food
• They absorb energy from sunlight
• Then use the energy to react with water and carbon dioxide to make glucose
• Energy is stored in glucose
• Oxygen is released as a waste product
• They use a green chemichal called Chlorophyll in Chloroplasts to perform photo synthesis

                                       Light

Water + Carbon dioxide  ------>       Glucose + Oxygen

                                     Chlorophyll

Photosynthesis takes place in the leaves because they are thin, have a large surface area, have small holes called the stomata - lets in carbon dioxide and lets oxygen out, have tiny tubes called xylem - to carry water and minerals up from the roots, have other tiny ubes called phloem - arry glucose away for storage.

Photosynthesis is important because plants and animals depend on eachother, they provide animals with food - glucose - and oxygen, animals provide plants with carbon dioxide, most animals on earth depend on plants for glucose and oxygen to breathe, the most glucose and oxygen are produced by plants in the rain.

Humans and their food supply

• For humans a good food supply is important, food supply depends on how organisms transfer energy from one to another
• Insects pollinate flowers so seeds and fruit can grow and be used as food by other animals. They rely on insects to pollinate their crops
• Insecticides can kill harmful insects and bugs, but can also kill useful polinators

Interpendance of organisms

• To show how organisms depend on eachother its best to draw a fod web - turn over
• the're made of different food chains, they describe what eats what in a community
• Food webs show how they depend on one another for food
• Producers are plants. they produce food by photosynthesis. Consumers are animals. they consume food for energy

Organisms and the Enviroment  - turn over for diagram

Sometimes poisonous waste an get  into an eco system: 1) plants at the bottom of the food web absorb the poison. 2) The poison is passed on to the animals that feed upon them. 3) Because these animals eat lost of plants they absorb more of the poison. 4) The poison accumalates as it passes up the food web; this is called bioaccumulation. 5) Eventually there is enough poison in the animals at the top of the food chain to kill them

• Most living organisms are different from one another. This is called variation.
• Different species have different characteristics.
• Different species survive in the same ecosystem because they are adapted to survive in different parts of the ecosystem.
• For example, different parts of the ecosystems are called niches
• Fish libe in water so they have gills; birds fly, so they have wings.
• Variation means that certain members of a species are more likely to survive when the enviroment changes.

Breathing

• Breathing involves moving air into and out of the lungs
• When breathing in: 1) Ribs move in and out 2) Diaphram flattens and moves down 3) Space inside the lungs increases 4)This increases the volume and reduces the pressure 5)Air rushes into the lungd from outside
• When breathing out: 1) Ribs move down and in. 2) Diaphram moves up. 3) Space inside the lungs decreases. 4) This decreases the volume and increses the pressure. 5) Air is pushedout of the lungs

Gas Exchange

The lungs are made of millions of tiny air sacs called alveoli. They are: Thin, Moist, Have a good blood supply, Have a large surface area. Gas Exchange is when: Carbon dioxide leaves the lungs and enters the lungs to be breathed out, Oxygen leaves the lungs and enters the blood. Gas exchange happens through the thin walls of the air sacs. The exchange happens because of diffusion.

Things that affect our breathing

• Exercise - Increases lung size and it improves gas exchange
• Asthma - Causes breathing tubes (bronchioles) to narrow, making breathing difficult
• Smoking - Damages the breathing tubes so that mucus builds up. This causes a cough, makes breathing more difficult and makes infections more likely. In the long term can cause emphysema and lung cancer.

Using a light microscope

• Cells are too small to see with th naked eye. Using a light microscope helps us too see and draw cells.

A

PLANT

CELL

How plant and animal cells work

• Membrane - Controls whet enters and leaves the cell - Animal cell , yes. Plant cell, yes
• Cytoplasm - Place where lots of chemical reactions take place - Animal cell, yes. Plant cell , yes
• Nucleus - Stores infomation (DNA) and controls what happens in the cell - Animal cell, yes. Plant cell, yes
• Mitochondria - Release energy from food (glucose) by aerobic respiration - Animal cell, yes. Plant cell, yes
• Cell wall - Made from cellulose and gives rigid support to the cell - Animal cell, no. Plant cell, Yes
• Vacuole - Inflates the cell which provides support to cell - Animal cell, no. Plant cell, usually
• Chloroplast - Contains green chlorophyll that changes sunlight energy into glucose food energy - Animal cell, no. Plant cell, yes

Diffusion

• Diffusion is one of the ways that substances enter and leave the cells
• In an animal cell, oxygen and glucose diffuse through the membrane into the cell. This is because there is more oxygen and glucose outside the cell than there is inside.
• Carbon dioxide and waste products diffuse out of the cell into the blood
• In a plant cell, carbon dioxide diffuses in. Oxygen and glucose diffuse out.

Unicelular organisms

• Unicellular organisms have only one cell.
• Euglena has a long whip-like structure to help it move through water.
• Amoeba can make finger-like projections to catch food.

Organisation of cells

• Cells of the same type and are carrying out same operation are grouped together to form a tissue. Differypes of tissues are grouped together to form organs. Different types of organs are grouped together to form organ systems. Organ systems are grouped together to form an organism 
• Examples of cell and organ systems: bone cells in skeletal system, blood cells in transport system, nerve cells in the nervous system ans sperm cells in the reprodctive system

• Combustion is the reaction between a fuel and oxygen 
• Carbon dioxide and water are generally produced as waste products when the fuel is a hydrocarbon 
• Energy is released as heat and light

• Some compounds break down into new molecules when heated; they don't react with oxygen in the air.
• This is called Thermal Decomposition
• An example is chalk, which has the chemical name calcium carbonate

• Wen a substances gain oxygen in a reaction it is called Oxidation 
• Loosing oxygen in a reaction is calles Reduction 
• For example, Carbon can be Oxidized to form carbon dioxide 
• The reaction of iron with water and oxygen is a special form of oxidation, forming iron (III) oxide, which is known as rust
• Rusting requires oxygen and water. It happens faster when salt is dissolved in the water.

• Hydrogen 
• Helium
• Lythium 
• Berilium 
• Boron 
• Carbon 
• Nitrogen 
• Oxygen 
• Florine 
• Neon 
• Sulphur
• Magnesium
• Alluminium
• Sillicone
• Phospherus
• Sulpher
• Chlorine 
• Argon
• potassium 
• Calcium

Partilcle Model

solid -> liquid -> gas

->

->

->

Changes of state

solid to liquid = melting 

liquid to gas = evaporating

gas to liquid = condensing

liquid to solid = freezing

Floating or sinking

You can decide is smething will float by working out it's density,and the density of the fluid. if the ddensity is less than the fluid density it will float

Light travels as transverse waves. It travels much faster then sound, and does not need a substance to travel through.

Light travels through transparent objects but not through opaque objects. Shadows are made when light is blocked by an object. Opaque objects block all light. Translucent objects allow som elight to pass through, but is scatteres so you do not see a clear image.

Light rays are scattered by rough surfaces, you can't see an image in an object with a rough srface.

Mirrors and shiny materials suchas polished metals reflect light evenly. This is called specular reflection. The angle of incidence is equal to the angle of reflection - this is known as the law of reflection. Angles are measured between the light rays and the normal (a line drawn at right angles to the reflecting surface)

When ight hits something transparent it changes speed and direction. this is called refraction.