Characteristics of living things

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What makes something alive?

Big idea: Systems. A living thing is a system: lots of parts working together to keep it alive.
Related concept: Function. Each life process has a job (a function) that helps the organism survive.
Global context: Identities and relationships. We ask what it means to be a living thing, and how we are related to every other living thing on Earth.
An organism is any living thing, from a tiny bacterium to a blue whale.
Scientists cannot just say "it looks alive". They use a checklist of life processes. A living thing carries out all of them.

The seven life processes

Remember them with MRS GREN: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.
Movement: living things move their bodies or parts of their bodies. Animals walk, swim or fly. Plants move too, for example a flower opening or a shoot growing towards light.
Sensitivity: detecting changes in the surroundings (stimuli) and responding to them. Your eyes detect light, and your pupils get smaller in bright light.
Growth: a permanent increase in size, made by building new material. Eating a big meal does not count as growth.
Reproduction: making new living things of the same kind. Without it, a type of organism would die out.

The Seven Life Processes (MRS GREN)

Respiration, excretion and nutrition

Respiration is a chemical reaction in cells that releases energy from food (glucose). Every living cell does it, all the time.
Respiration is not the same as breathing. Breathing moves air in and out of your lungs; respiration happens inside cells.
Excretion is removing waste made by the body's own chemical reactions, such as carbon dioxide (breathed out) and urea (in urine).
Excretion is not the same as egestion. Egestion is getting rid of food that was never absorbed, as faeces.
Nutrition is taking in or making the materials and energy needed to live. Animals eat food. Plants make their own food by photosynthesis.

Living, non-living and once-living

Living: carries out all seven life processes now, such as a cat, an oak tree or a mushroom.
Non-living: never was alive, such as a rock, water, plastic or a cloud.
Once-living: was part of a living thing but is now dead or made from something dead, such as wood, paper, cotton or a dead leaf.
Non-living things can do some life-like things. A crystal can grow and a river can move, but they do not do all seven processes.
To test a seed, see if it grows when given water and warmth. A seed that does is alive, but a seed that never does may be dead.

Edge cases: viruses and fire

Scientists still argue about viruses. A virus is a tiny package of genetic material in a protein coat. It is not made of cells.
A virus can reproduce only inside a host cell. Outside one, it does nothing at all. It does not respire, grow or excrete on its own.
Because it only shows some life processes, and only in a host, many scientists treat viruses as on the edge of being alive.
Fire seems to move, grow, use oxygen and give off waste gases. But it is not made of cells, does not reproduce with genetic material and has no sensitivity as living things do.
Edge cases show that our checklist is a model. Models are useful, but nature does not always fit them.

A virus particle

Think like a scientist: a fair test

A fair test changes only one thing and keeps everything else the same, so you know what caused any difference.
The thing you change is the independent variable. The thing you measure is the dependent variable. Everything you keep the same is a control variable.
Example: to test if light affects how tall cress seedlings grow, the independent variable is the amount of light and the dependent variable is seedling height.
Control variables here: the amount of water, the temperature, the type and number of seeds, and the soil.
Repeat the test with several seedlings, then calculate a mean. One seedling could grow tall just by chance.
Inquiry task: plan a fair test to find out whether temperature affects how quickly seeds germinate (start to grow). Name your three kinds of variable, say how you will measure the result, and say how you will make your results reliable.

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1.What does the letter M stand for in MRS GREN?
Easy
- AMetabolism
- BMovement
- CMutation
- DMuscle
2.How many life processes are in the MRS GREN list?
Easy
- AFive
- BSix
- CSeven
- DEight
3.Which life process releases energy from food?
Easy
- ANutrition
- BExcretion
- CGrowth
- DRespiration
4.What does sensitivity mean as a life process?
Easy
- ABeing easily upset
- BDetecting changes around you and responding to them
- CGetting rid of waste
- DMaking new living things
5.Which of these is a living thing?
Easy
- AA mushroom
- BA cloud
- CA river
- DA rock
6.Which of these is non-living?
Easy
- ASeaweed
- BMoss
- CSand
- DA coral polyp
7.A sunflower turns to face the Sun through the day. Which life process does this show best?
Medium
- AExcretion
- BRespiration
- CReproduction
- DSensitivity
8.Which of these is an example of excretion?
Medium
- AA dog breathing out carbon dioxide
- BA dog eating its dinner
- CA dog burying a bone
- DA dog having puppies

Soal lainnya

9.Why is breathing not the same thing as respiration?
Medium
- ABreathing happens in cells and respiration happens in lungs
- BOnly animals breathe but only plants respire
- CBreathing moves air in and out; respiration releases energy in cells
- DThey are the same, just with two names
10.Plants do not eat food. How do they carry out nutrition?
Medium
- AThey make their own food by photosynthesis
- BThey absorb ready-made glucose from the air
- CThey do not need nutrition
- DThey eat tiny soil animals
11.Which of these is a once-living thing?
Medium
- AA plastic bottle
- BA pebble
- CA living oak tree
- DA wooden table
12.Which of these best describes growth as a life process?
Medium
- AGetting heavier after a large meal
- BA permanent increase in size made by building new material
- CMoving from one place to another
- DChanging colour in the sunshine
13.What is reproduction?
Medium
- AMaking new living things of the same kind
- BCopying a drawing of an animal
- CGrowing larger over many years
- DGetting energy from glucose
14.Which of these is an example of movement in a plant?
Medium
- AA leaf turning brown
- BA root absorbing water
- CA seed being eaten
- DA flower opening in the morning
15.Which pair of things do most living things need for respiration?
Medium
- ANitrogen and water
- BCarbon dioxide and light
- COxygen and glucose
- DProtein and salt
16.Why is a virus often called an edge case?
Medium
- AIt is too big to see
- BIt is always found on the edges of cells
- CIt has only one cell
- DIt only reproduces inside a host cell and is not made of cells
17.A salt crystal in salty water gets bigger over time. Why is it still not alive?
Hard
- AIt only grows by adding material from outside and does not carry out the other life processes
- BIt is too small to be alive
- CCrystals cannot be seen without a microscope
- DSalt is a poison
18.Fire moves, grows, uses oxygen and gives off waste gases. Why do scientists still say it is not alive?
Hard
- AIt gives off heat
- BIt is not made of cells and does not carry out all the life processes as a living thing does
- CIt is too hot to touch
- DIt only burns in daylight
19.A dog and a cactus are both living. Which life process is carried out in the most different way in the two?
Hard
- ARespiration
- BNutrition
- CExcretion
- DGrowth
20.You find a dry seed. Which result would show it is alive and not just once-living?
Hard
- AIt floats in water
- BIt is hard and brown
- CIt rattles when shaken
- DIt grows a root when given water and warmth
21.A student tests whether the amount of light affects how tall bean seedlings grow. What is the independent variable?
Medium
- AThe amount of light
- BThe height of the seedlings
- CThe type of seed
- DThe volume of water
22.Which set-up is a fair test of whether water affects seed germination?
Hard
- ADish A: 10 seeds, water, warm and light. Dish B: 10 seeds, no water, cold and dark
- BDish A: 10 seeds, water, warm. Dish B: 10 seeds, no water, same warmth and light
- CDish A: 20 seeds with water. Dish B: 5 seeds with no water, all in the same place
- DDish A: 10 bean seeds, water. Dish B: 10 cress seeds, no water
23.One seedling in the dark grew 4 cm and one seedling in the light grew 9 cm. A student says: "Light always makes plants grow taller." What is the main weakness of this conclusion?
Hard
- ASeedlings cannot grow in the dark
- BOnly one seedling was used for each condition, so the result could be chance
- CThe light was too bright
- DHeight is not a good thing to measure
24.In an experiment on seedling growth, which of these is the dependent variable?
Medium
- AThe temperature of the room
- BThe height of the seedlings
- CThe number of seeds sown
- DThe amount of light given
25.Which of these are life processes? (select all that apply)
Medium
- AGrowth
- BReproduction
- CExcretion
- DRusting
- EMelting
26.Which of these are living things? (select all that apply)
Medium
- AAn oak tree
- BYeast
- CA wooden chair
- DA mushroom
- EA pebble
27.Which statements about viruses are true? (select all that apply)
Hard
- AThey are made of a single cell
- BThey can reproduce only inside a host cell
- CThey are not made of cells
- DThey carry genetic material
- EThey respire on their own
28.Which of these are waste products that living things excrete? (select all that apply)
Medium
- ACarbon dioxide
- BUrea
- CUndigested fibre
- DGlucose
29.Plants carry out respiration.
Easy
True or false?
30.Only animals can move.
Easy
True or false?
31.Plants can detect light.
Easy
True or false?
32.Breathing and respiration mean exactly the same thing.
Medium
True or false?
33.A dead leaf is non-living because it has never been alive.
Medium
True or false?
34.Getting rid of undigested food as faeces is called excretion.
Medium
True or false?
35.Excretion means removing waste made by the body's own chemical reactions.
Medium
True or false?
36.A virus can reproduce on its own outside a host cell.
Hard
True or false?
37.Match each life process to an example.
Easy
- Movement
- Respiration
- Sensitivity
- Excretion
- Removing urea in urine
- A cheetah sprinting
- Releasing energy from glucose
- A shoot bending towards a window
38.Match each thing to the group it belongs in.
Medium
- An earthworm
- Granite
- A sheet of paper
- Non-living
- Once-living
- Living
39.Match each life process to how a plant carries it out.
Hard
- Nutrition
- Reproduction
- Growth
- Sensitivity
- Roots growing downwards
- Making glucose in the leaves
- Producing seeds in pods
- A shoot getting taller
40.Put the seven life processes in the order they appear in MRS GREN.
Medium
- Growth
- Movement
- Nutrition
- Sensitivity
- Reproduction
- Respiration
- Excretion
41.Put these steps of planning a fair test in a sensible order.
Hard
- Repeat the test and calculate a mean
- Keep every other variable the same
- Choose one variable to change
- Measure the result in each set-up
- Write a conclusion using your results
42.Complete the sentence.
Easy
The life process that releases energy from food in cells is called ____.
43.Complete the sentence.
Medium
Removing waste made by the body's own chemical reactions is called ____.
44.Complete the sentence.
Medium
Wood is described as ____-living because it came from a tree that was alive.
45.Complete the sentence.
Hard
A virus can only reproduce inside a ____ cell.
46.A cress seedling is 5 mm tall. It then grows 3 mm every day for 8 days. How tall is it after 8 days, in mm?
Medium
47.Explain the difference between a living thing and a once-living thing. Give one example of each.
Medium
48.Explain why scientists find it hard to decide whether a virus is living or non-living.
Hard
49.Plan a fair test to find out whether temperature affects how quickly cress seeds germinate. State what you change, what you measure and two things you keep the same.
Hard
50.A student says a car is alive because it moves, uses fuel and gives out waste gases. Evaluate this claim.
Hard

Catatan ulasan

## Life processes - **MRS GREN**: movement, respiration, sensitivity, growth, reproduction, excretion, nutrition. Living things do all seven. - **Respiration** releases energy from glucose in cells; it is not breathing. - **Excretion** removes waste made by the body; **egestion** removes undigested food. - Plants make food by **photosynthesis**. ## Sorting - **Living**, **non-living** and **once-living** (wood, paper, dead leaves). ## Edge cases - A **virus** is not made of cells and reproduces only inside a **host cell**. **Fire** grows and uses oxygen but is not alive. ## Inquiry - Fair test: change one **independent variable**, measure the **dependent variable**, control the rest, and repeat.

Organism: Any living thing.
Movement: Moving the whole body or parts of the body.
Respiration: A reaction in cells that releases energy from food such as glucose.
Sensitivity: Detecting changes in the surroundings and responding to them.
Stimulus: A change in the surroundings that an organism can detect.
Growth: A permanent increase in size made by building new material.
Reproduction: Making new living things of the same kind.
Excretion: Removing waste made by the body's own chemical reactions.
Nutrition: Taking in or making the materials and energy needed to live.
Once-living: Something that came from a living thing but is now dead or made from something dead.
Virus: A tiny particle of genetic material in a protein coat that can only reproduce inside a host cell.
Independent variable: The variable you change in an investigation.
Dependent variable: The variable you measure in an investigation.
Control variable: A variable you keep the same to make a test fair.

Kartu flash

What does MRS GREN stand for?

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

What is respiration?

A reaction in cells that releases energy from food such as glucose.

How is breathing different from respiration?

Breathing moves air in and out of the lungs; respiration happens in cells and releases energy.

What is sensitivity?

Detecting changes (stimuli) in the surroundings and responding to them.

Give an example of movement in a plant.

A flower opening, or a shoot growing towards light.

What is growth?

A permanent increase in size, made by building new material.

What is reproduction?

Making new living things of the same kind.

What is excretion?

Removing waste made by the body's own chemical reactions, such as carbon dioxide and urea.

What is egestion?

Getting rid of undigested food as faeces. It is not excretion.

How do plants carry out nutrition?

They make glucose by photosynthesis using light, water and carbon dioxide.

What is a once-living thing?

Something that came from a living thing, such as wood, paper or a dead leaf.

Give one example each of living, non-living and once-living.

Living: a cat. Non-living: a rock. Once-living: a wooden table.

Why is a virus an edge case?

It is not made of cells and can only reproduce inside a host cell.

Why is fire not alive?

It is a chemical reaction. It is not made of cells and does not reproduce or respond like an organism.

What is the independent variable?

The one thing you change in an investigation.

What is the dependent variable?

The thing you measure to see the effect of the change.

What makes a test fair?

Changing only one variable and keeping all the control variables the same.

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