From cells to organ systems

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Lektionsnotizen

Big idea: one body, many jobs

Big idea: the key concept is Systems, the related concept is Form (how something's shape suits its job) and the global context is Identities and relationships: what makes up a living body.
A unicellular organism is a single cell that does every life process for itself.
Your body has trillions of cells. They cannot all do everything, so they share the work: this is called division of labour.
Cells that have a shape and parts that suit one job are specialised cells.
Cells are grouped into tissues, then organs, then organ systems, all working together as one organism.

Single-celled and multicellular organisms

Specialised animal cells

A red blood cell is a flattened biconcave disc with no nucleus. The shape gives a large surface area, and the space is filled with haemoglobin, which carries oxygen.
A nerve cell (neurone) is very long, with a long axon and branched ends. It carries electrical impulses from one part of the body to another.
A sperm cell has a tail (flagellum) for swimming, a streamlined head, and many mitochondria to release the energy for the tail to beat.
A ciliated cell has tiny hairs called cilia that sweep mucus along, for example in the windpipe.
The pattern is always the same: a feature that helps with the job. Scientists call a helpful feature an adaptation.

Four specialised human cells

Specialised plant cells

A root hair cell has a long, thin projection that pushes between soil particles. It gives a large surface area to absorb water and dissolved minerals.
A palisade cell is packed with chloroplasts, which contain chlorophyll to capture light for photosynthesis.
Palisade cells are tall and closely packed near the top of the leaf, where they get the most light.
Root hair cells have no chloroplasts because they are underground, where there is no light for photosynthesis.
Plant cells also have a cell wall and a nucleus. Their specialised features are added to the basic plant cell.

Palisade cells in leaf tissue, with organelles labelled

Tissues and organs

A tissue is a group of similar cells that work together to do the same job. Muscular tissue contracts, glandular tissue makes juices and epithelial tissue covers surfaces.
An organ is a group of different tissues that work together to do a particular job.
The stomach is an organ: muscular tissue churns the food, glandular tissue makes digestive juices and epithelial tissue covers the inside and outside.
Plants have organs too. A leaf contains palisade tissue, epidermis and xylem, all working together for photosynthesis.
Other examples of organs are the heart, the lungs, the brain and the kidneys.

Tissues of the stomach

Organ systems and the whole organism

An organ system is a group of organs that work together to do a major job.
The digestive system breaks down food. The circulatory system moves blood around the body. The nervous system sends messages. The respiratory system takes in oxygen.
The systems depend on each other. The digestive system passes nutrients into the blood, and the circulatory system delivers them to every cell.
The levels of organisation in order are cell, tissue, organ, organ system, organism.
If one part fails, the levels above it are affected. A problem with the cells of the lungs can reduce the oxygen reaching the whole organism.

Levels of organisation: cell to organism

Think like a scientist: does cell size matter?

Cells take in materials through their surface. A cell with a large surface area compared with its size can take in materials more quickly.
You can model this with jelly (agar) cubes of different sizes soaked in coloured dye for the same time, then cut open to see how far the dye has reached.
The independent variable is the size of the cube. The dependent variable is how far the dye has travelled in. Control variables are the time in the dye, the strength of the dye and the temperature.
Inquiry task: write a plan to test this model. Say what you will change, measure and keep the same, and explain how you will make your results reliable (for example repeating the test and calculating a mean).
Evaluate: jelly is only a model. List one way the jelly cubes are like a cell and one way they are not.

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1.What does it mean if a cell is specialised?
Easy
- AIt can do every job in the body equally well
- BIt is always larger than the cells around it
- CIt has a shape and parts that suit one job
- DIt has no cell membrane around it
2.Which cell carries oxygen around the body?
Easy
- ANerve cell
- BSperm cell
- CPalisade cell
- DRed blood cell
3.Which type of cell carries electrical messages around the body?
Easy
- ARed blood cell
- BRoot hair cell
- CPalisade cell
- DNerve cell
4.Which plant cell absorbs water and minerals from the soil?
Easy
- APalisade cell
- BRoot hair cell
- CSperm cell
- DRed blood cell
5.Which cell swims using a tail?
Easy
- ANerve cell
- BRed blood cell
- CSperm cell
- DPalisade cell
6.Which leaf cells contain lots of chloroplasts for photosynthesis?
Easy
- ARoot hair cells
- BNerve cells
- CRed blood cells
- DPalisade cells
7.Why does a red blood cell have no nucleus?
Medium
- AIt lets the cell divide faster while it is in the blood
- BIt leaves more room inside for haemoglobin to carry oxygen
- CIt makes the cell light enough to float in blood
- DIt stops the cell using up the oxygen it carries
8.How does the biconcave disc shape help a red blood cell?
Medium
- AIt lets the cell swim against the flow of the blood
- BIt lets the cell store food for later
- CIt makes the cell stick to the walls of blood vessels
- DIt gives a large surface area for fast oxygen uptake

Mehr Fragen

9.Why is a nerve cell very long?
Medium
- AOne cell can carry a message a long way
- BIt can collect more sunlight for food
- CIt can swim much faster than others
- DIt can store a lot more oxygen
10.Why does a sperm cell contain many mitochondria?
Medium
- AThey make food by photosynthesis
- BThey store the cell's genetic information
- CThey release the energy needed to beat the tail
- DThey make the head more streamlined
11.What is the job of the long projection on a root hair cell?
Medium
- AIt carries electrical messages to the stem
- BIt gives a large surface area to absorb water
- CIt makes food for the plant using light
- DIt helps the cell swim through the soil
12.Why are palisade cells found near the top of a leaf?
Medium
- AThey are closest to the roots
- BThey are protected from sunlight there
- CThey are close to the light that photosynthesis needs
- DThey can lose water more slowly there
13.What is a tissue?
Easy
- AA single cell that has a very special job
- BA group of different organs working together
- CA thin piece of paper used in a laboratory
- DA group of similar cells that do the same job
14.What is an organ?
Easy
- AA group of different tissues working together
- BA group of similar cells doing the same job
- CA single cell that has grown very large
- DA group of several organ systems together
15.What is an organ system?
Easy
- AA group of similar cells doing the same job
- BA group of organs that work together
- CA single organ with lots of tissues
- DAnother name for an organism
16.Which of these is the smallest level of organisation?
Easy
- ATissue
- BOrgan
- CCell
- DOrganism
17.Which of these is an organ?
Easy
- AA red blood cell
- BThe heart
- CThe nervous system
- DMuscle tissue
18.The stomach, small intestine and liver all belong to which organ system?
Easy
- ADigestive system
- BCirculatory system
- CNervous system
- DRespiratory system
19.Which organ system contains the brain, the spinal cord and the nerves?
Easy
- ASkeletal system
- BDigestive system
- CCirculatory system
- DNervous system
20.Which type of tissue in the stomach wall makes the digestive juices?
Hard
- AMuscular tissue
- BEpithelial tissue
- CBone tissue
- DGlandular tissue
21.Why is a leaf an organ and not a tissue?
Hard
- AIt is made of only one kind of cell
- BIt is made of several organ systems
- CIt is made of several different tissues working together
- DIt is too small to be a tissue
22.A student writes: 'A palisade cell is a tissue.' Which correction is best?
Hard
- AA palisade cell is an organ, made of several tissues
- BIt is one cell, and many together make a tissue
- CA palisade cell is an organ system inside the leaf
- DA palisade cell is a tissue only when it is alive
23.Why do large organisms such as humans need specialised cells?
Hard
- ACells share out jobs, and inner cells cannot reach the outside
- BSpecialised cells never need energy, unlike other cells
- CLarge organisms cannot make any new cells at all when they grow
- DSpecialised cells are always all exactly the same size and shape
24.Which of these are features of a red blood cell? (select all that apply)
Medium
- AContains haemoglobin
- BHas a biconcave disc shape
- CHas a large nucleus
- DHas no nucleus
- EHas a long tail
25.Which of these are found in a palisade cell? (select all that apply)
Medium
- AA flagellum
- BChloroplasts
- CA nucleus
- DA cell wall
- EA biconcave shape
26.Which of these are organs? (select all that apply)
Medium
- AStomach
- BA red blood cell
- CLungs
- DThe nervous system
- EHeart
27.Which of these are types of tissue? (select all that apply)
Hard
- AMuscular tissue
- BThe brain
- CEpithelial tissue
- DA sperm cell
- EGlandular tissue
28.A nerve cell is an example of a specialised cell.
Easy
True or false?
29.Red blood cells contain a large nucleus.
Easy
True or false?
30.A group of similar cells doing the same job is called an organ.
Easy
True or false?
31.Palisade cells contain chloroplasts.
Easy
True or false?
32.In a large organism every cell looks exactly the same.
Easy
True or false?
33.Root hair cells are found in the leaves of a plant.
Easy
True or false?
34.The heart is made of more than one type of tissue.
Hard
True or false?
35.One organism can contain several organ systems.
Medium
True or false?
36.The shape of a specialised cell is linked to the job it does.
Medium
True or false?
37.Match each cell to its job.
Easy
- Red blood cell
- Nerve cell
- Sperm cell
- Root hair cell
- Palisade cell
- Absorbs water and minerals
- Carries oxygen
- Makes food by photosynthesis
- Carries electrical impulses
- Swims to reach an egg cell
38.Match each cell to a feature that helps it do its job.
Medium
- Red blood cell
- Nerve cell
- Sperm cell
- Palisade cell
- Root hair cell
- Tail and many mitochondria
- Long, thin projection
- Long axon with branched ends
- Many chloroplasts
- Biconcave shape and no nucleus
39.Match each level of organisation to an example.
Medium
- Tissue
- Organ
- Organ system
- Organism
- Stomach
- A human being
- Muscular tissue
- Digestive system
40.Put these levels of organisation in order, from smallest to largest.
Easy
- Organ
- Organism
- Cell
- Organ system
- Tissue
41.Put these parts of a plant in order, from smallest to largest.
Hard
- Shoot system
- Palisade cell
- Whole plant
- Leaf
- Palisade tissue
42.Put these in order for the circulatory system, from smallest to largest.
Medium
- Heart muscle tissue
- Circulatory system
- Heart muscle cell
- Human
- Heart
43.A group of similar cells that do the same job is called a ___.
Easy
A group of similar cells that do the same job is called a ____.
44.Several different tissues working together make an ___.
Easy
Several different tissues working together make an ____.
45.Red blood cells contain a red substance called ___ that carries oxygen.
Medium
Red blood cells contain a red substance called ____ that carries oxygen.
46.The long projection on a root hair cell increases its surface ___.
Medium
The long projection on a root hair cell increases its surface ____.
47.A sperm cell has many ___ to release the energy it needs for swimming.
Medium
A sperm cell has many ____ to release the energy it needs for swimming.
48.A student cuts jelly (agar) into cubes of different sizes. She soaks every cube in the same coloured dye for 10 minutes, then cuts each cube open and measures how far the dye has reached. Which is the independent variable (the one she changes on purpose)?
Medium
- AThe time the cubes spend in the dye
- BHow far the dye has travelled in
- CThe size of the cube
- DThe colour of the dye
49.A student cuts jelly (agar) into cubes of different sizes. She soaks every cube in the same coloured dye for 10 minutes, then cuts each cube open and measures how far the dye has reached. Which is the dependent variable (the one she measures)?
Medium
- AHow far the dye has travelled into each cube
- BThe size of the cube
- CThe temperature of the room
- DThe type of dye
50.A student cuts jelly (agar) into cubes of different sizes. She soaks every cube in the same coloured dye for 10 minutes, then cuts each cube open and measures how far the dye has reached. Which of these must she keep the same to make it a fair test? (select all that apply)
Hard
- AThe time in the dye
- BThe size of the cube
- CThe kind and strength of dye
- DThe temperature of the dye
- EThe distance the dye reaches
51.In the same experiment the dye reached the centre of the smallest cube but only the outer layer of the biggest cube. Which conclusion is best supported by this result?
Hard
- ABigger cubes are always better because they can hold a lot more dye
- BSmall cubes took in dye faster, so small cells may take in materials faster
- CEvery living cell takes in dye at exactly the same speed as jelly
- DDye cannot move into any jelly cube that is bigger than 1 cm wide
52.Put these steps of a fair test in a sensible order.
Medium
- Repeat the test and calculate a mean
- Decide which variable to change and which to measure
- Write a conclusion that matches the results
- Keep all the other variables the same
- Carry out the test and record the measurements
53.Explain how the digestive system and the circulatory system work together.
Hard
54.Explain how a red blood cell is adapted to carry oxygen.
Medium
55.Explain why the stomach is an organ and not a tissue.
Hard

Lernnotizen

## Specialised cells - A **specialised cell** has features (**adaptations**) that suit one job. - **Red blood cell:** biconcave, no nucleus, **haemoglobin**, carries oxygen. - **Nerve cell:** long axon and branched ends, carries impulses. - **Sperm cell:** tail and many mitochondria. - **Root hair cell:** long projection, absorbs water and minerals. - **Palisade cell:** many chloroplasts, photosynthesis. ## Levels of organisation - **Cell**, then **tissue** (similar cells), then **organ** (different tissues), then **organ system** (several organs), then **organism**. - Examples: stomach (organ), digestive system (organ system), leaf (plant organ). ## Think like a scientist - In a fair test, change one variable, measure one, and control the rest. Repeat and take a mean. - Jelly cubes are a model for cell size, but a model is never exactly like a real cell.

Specialised cell: A cell with a shape and parts that suit it to one particular job.
Adaptation: A feature that helps a cell or organism do its job or survive.
Red blood cell: A biconcave disc with no nucleus and lots of haemoglobin, which carries oxygen.
Haemoglobin: The red substance in red blood cells that binds to oxygen.
Nerve cell (neurone): A long cell with branched ends that carries electrical impulses.
Root hair cell: A root cell with a long projection that absorbs water and minerals from the soil.
Palisade cell: A leaf cell packed with chloroplasts, specialised for photosynthesis.
Sperm cell: A cell with a tail, many mitochondria and a streamlined head.
Tissue: A group of similar cells that work together to do the same job.
Organ: A group of different tissues working together to do a particular job.
Organ system: A group of organs that work together to carry out a major function.
Organism: A whole living thing, made of organ systems working together.
Surface area: The total area of the outside of a cell or object, which controls how fast materials can move in.

Karteikarten

What is a specialised cell?

A cell with a shape and parts that suit it to one particular job.

Name two adaptations of a red blood cell.

Biconcave disc shape (large surface area) and no nucleus (more room for haemoglobin).

What does haemoglobin do?

It binds to oxygen so that red blood cells can carry it around the body.

How is a nerve cell adapted to its job?

It is long, with a long axon and branched ends, so it can carry impulses over a distance.

How is a sperm cell adapted to its job?

It has a tail to swim, many mitochondria for energy, and a streamlined head.

How is a root hair cell adapted?

Its long, thin projection gives a large surface area for absorbing water and minerals.

How is a palisade cell adapted?

It has lots of chloroplasts for photosynthesis and sits near the top of the leaf.

What is a tissue?

A group of similar cells that work together to do the same job.

Name three types of tissue.

Muscular, glandular and epithelial tissue.

What is an organ?

A group of different tissues working together to do a particular job.

What is an organ system?

A group of organs that work together to carry out a major function.

Give the levels of organisation from smallest to largest.

Cell, tissue, organ, organ system, organism.

Name the three tissues in the stomach.

Muscular, glandular and epithelial tissue.

Why is a leaf an organ?

It is made of several different tissues, such as palisade tissue and epidermis, working together.

Why do large organisms need specialised cells?

Different cells do different jobs well, and cells deep inside cannot reach the outside themselves.

In the jelly cube test, what is the independent variable?

The size of the cube.

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