How Science Works Skills

Aim

Pupils observe feeding in single-celled organisms, making use of digital technology to magnify and transmit images and to capture and record information. The difficulties of working with microscopic living material will be considered.

How Science Works skills

Pupils record observations, comparisons and measurements using tables and barcharts, and begin to plot points to form simple graphs. (Level 4)
Pupils begin to relate conclusions to patterns in data, including graphs, and to scientific knowledge and understanding. (Level 4)
Pupils communicate conclusions using appropriate scientific language. (Level 4)

Key concepts and processes

KP2.2a, KP2.3a

Equipment

digital microscope or light microscope with digital camera such as flexcam attached; LED illumination preferred

digital projector

cultures of various organisms to show a range of feeding methods, such as Amoeba, Stentor, Paramoecium

digital video capture software, such as that provided with web cams or digital microscopes

access to computers

Safety notes

If using pond water rather than cultures from biological suppliers be aware of the risks of infection.

Running the activity

1This activity needs significant preparation time if you are using fresh material, which is the preferred option. The most reliable technique is to capture several short (10 second) digital video clips of feeding organisms which can then be used in the lesson, so that live material is only essential for the introductory phase. Suitable organisms can be found in pond water if no cultures are available from suppliers. Microscopes illuminated by LED enable living material to survive for much longer periods than incandescent bulb illumination.

Alternatively videos of feeding protozoa can be found on the Internet, on community and specialist microscopy sites. Use search phrases that include specific protozoa with cilia, such as Paramecium, Stentor and Vorticella.

2Introduce the lesson by projecting an image from a digital microscope on a screen, and discuss what can be seens.

3Ask pupils to examine the image on their sheet and suggest possible food sources for Stentor, and how Stentor is adapted for feeding.

4Pairs of pupils then access pre-recorded video clips of feeding organisms via their own computer. Ask them to choose one organism from the video clips provided.

5Outline the task to the class. They are to produce a pictorial explanation of how their chosen organism feeds.

6Discuss a range of pupil responses to this task before focussing on how cells are adapted for survival – both protozoa cells and human cells.

Expected outcomes

Pupils extract information from a video clip and use it to produce an annotated diagram that shows how cells areadapted to carry out feeding.

Pupils obtain images from a video and annotate them to explain how cells have become adapted. Pupils will need to generate their own explanations for how the structures observed support the feeding process.

Answers

1A range of answers are possible which could include:

some way of making a current in the water (cilia)
a way of getting food into the cell
somewhere for the food to be digested (food vacuoles)
a ‘mouth’ (oral groove)
a way for the cell to move towards its food
a way for the cell to detect food.

2A range of answers are possible which could include:

where things need to be moved along tubes in the body, e.g. egg cells, dust in the wind pipe, mucus
where cells need to attack and ‘swallow’ other cells, e.g. white blood cells fighting infection
where cells need to engulf food particles, e.g. in the gut (in humans food is digested into soluble form before being absorbed into cells)
where cells need to be able to detect different chemicals, e.g. in the nose and mouth
where cells need to be able to move freely, e.g. through blood vessels to get to sites of infection.

This worksheet may have been altered from the original.