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Transcript

Year 7 Science Revision

DNA & Inheritance

&

The Structure of the Earth

The Atmosphere

  • the gases that surround a planet make up that planets atmosphere
  • Earth's Atmosphere
  • 78% Nitrogen
  • 21% Oxygen
  • 1% other gases - 0.04% Carbon Dioxide/0.9% Argon
  • Carbon Dioxide
  • burning fossil fuels - increase carboon dioxide in the atmosphere
  • deforestation - less photosynthesis - more carbon dioxide in the air

Chromosomes, DNA & Genes

The Earth

  • Most cells in the body have a nucleus
  • the nucleus is the control centre of the cell
  • the nucleus contains chromosomes
  • chromosomes are long lengths of DNA
  • Chromosomes carry genes
  • different genes control different characteristics

The Earth is divided into

  • The crust: the part we live on - thin outer layer of solid rock
  • The mantle: mostly solid - deep down it can flow very slowly (thick liquid)
  • The Core: the centre - made of Iron & Nickel
  • the Earth's Surface is broken into plates
  • they're able to move around slowly
  • the plates move suddenly - earthquake
  • there are 3 types of Rock
  • Sedimentary - layers laid down over millions of years stuck together by minerals
  • Igneous - lava above ground, magma below the surface
  • Metamorphic - heat & pressure over a long period of time

Environmental & Hereditary

Variation

  • different species have different genes
  • variation is the differences between living things
  • variation also exists within a species
  • hair colour
  • skin colour
  • eye colour
  • Hereditary: from your parents
  • Environmental: from your friends, neighbourhood, school etc.
  • variation can occur in plants
  • large leaf size - to help catch sunlight
  • small leaf size - to prevent water loss
  • Organisms with characteristics that make them better at competing are more likely to survive and reproduce
  • organisms compete for:
  • food
  • shelter
  • mates
  • water

Photosynthesis

  • when plants respire they take in oxygen & release carbon dioxide
  • during photosynthesis the plants take in carbon dioxide & release oxygen
  • without photosynthesis there would not be enough oxygen in the air
  • there would be too much carbon dioxide in the air also

Forces

Interdependence:

plants rely on animals for the carbon dioxide & animals rely on plants for the oxygen

Forces are usually pushes and pulls

  • cant be seen - but the effects can (eg. wind)
  • are measured in Newtons (N)
  • usually act in pairs (opposite forces)
  • they always act in a certain direction
  • Newton meter - measures forces

Food Chains & Webs

Forces

  • food chains/webs show the flow of energy in an ecosystem
  • food webs are 2 or more food chains interlinked
  • producer: makes its own food (plant)
  • primary consumer: eats plants (rabbit)
  • secondary consumer: eats primary consumer
  • tertiary consumer: eats secondary consumer
  • herbivore: eats plants only
  • carnivore: eats animals only
  • omnivore: eats both plants & animals

Dependence on other Organisms

Forces can make objects do 5 things

  • speed up/start moving
  • slow down/stop moving
  • change direction
  • turn
  • change shape

Forces can occur between objects that aren't touching

  • forces usually occur between objects that are touching
  • forces due to gravity, magnetism & static electricity are all non-contact forces
  • A change in 1 organism can affect other organisms
  • Poisons build up in food chains

Friction

  • tries to stop objects sliding past each other
  • it is always in the opposite direction to movement
  • to push an object out of your way - need to overcome friction
  • friction
  • 2 surfaces rubbing together
  • an object passing through air or water

air & water resistance are frictional forces

FORCES

Forces

Dependence

Atmospheric Pressure

  • at sea level, there is a lot of atmosphere above you
  • the atmosphere weighs a bit so it applies a high pressure
  • at the top of a mountain - less atmosphere above you - pressure is lower
  • the pressure in liquids increases with depth
  • an ecosystem is all the living organisms in one area, plus their environment
  • the organisms are interdependent
  • they need each other to survive
  • all living things depend on plants
  • almost all energy on Earth comes from the sun
  • Photosynthesis: plants make their own food
  • the energy gets passed on from plants to animals when animals eat the plants

Force diagrams

  • equal and opposite forces - stationary or moving at a steady speed
  • Accelerating - forward force is bigger
  • slowing down - backward force is bigger

Gravity

  • Gravity is a force that attracts all masses
  • the Earth & the moon are attracted by gravity
  • the Earth & the Sun are attracted by gravity
  • Mass is not a force - weight is
  • mass is an amount of stuff - weight is caused by the pull of gravity
  • mass of an object never changes - weight can
  • mass is measured in kg using an electric balance
  • weight is measured in newtons (N) using a newton meter
  • weight = mass X gravity

HSW

Independent Variable - what you change in your investigation

Dependent Variable - what you measure

Control Variable - what you keep the same in each experiment

Fair Test - only one variable changed in the experiment

Time - stop watch - seconds (s)

Force - Newton Meter - Newtons (N)

Length (distance) - ruler - m or cm

Temperature - thermometer - degrees celsius

Mean/average - be able to calculate

Anomaly - does not fit the pattern

Prediction - what you think will happen

THE EARTH & BEYOND & HSW

The Sun & Stars

  • the Earth moves around the Sun in an orbit
  • the Sun is a star
  • the Earth is a planet
  • the Sun is luminous (emit light)
  • the planets are not
  • a galaxy is a large group of stars
  • our galaxy is called the Milky Way
  • the Sun is our closest star
  • a light year is a unit of distance (not time)
  • a constellation is a group of stars that form a recognisable pattern
  • Orion
  • the Plough

Day & Night

  • the rotation of the Earth causes days & night
  • the Earth rotates about its axis - 24 hours
  • the imaginary line running from the North to the South Pole
  • facing the Sun - light - day time
  • facing away from the Sun - no light - night time

The Seasons

  • takes 1 year (365.25 days) to orbit the Sun
  • the seasons are caused by the tilt of the Earths axis
  • Summer - Earth tilted towards the sun - Suns rays more concentrated - longer, warmer days
  • Winter - Earth tilts away from the Sun - Suns rays are more spread out - shorter, colder days
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