Investigating inheritance, chromosomes, DNA and genes
Inheritance, variation and natural selection can be difficult concepts to grasp, but actively engaging students in practical work can help them to construct a clearer understanding.
Visit the practical work page to access all resources and lists focussing on practical work in secondary science: www.nationalstemcentre.org.uk/sciencepracticals
Introducing ideas about inheritance
From 2014, students should learn about heredity as the process by which genetic information is transmitted from one generation to the next, and about the variation between individuals within a species, including measurement and graphical representation of variation.
This activity helps students to consider the characteristics which can be inherited and distinguish them from environmental variation.
A number of characteristics are suggested for the investigation, although it's important to be sensitive about issues related to body image and to avoid innappropriate comments about individuals. The teaching notes provide useful advice and suggests a good ASE publication - the Language of Measurement - which looks at key vocabulary in investigations.
Make Your Own Mucus and Extracting DNA
There is an activity sheet in this resource which describes a simple method for extracting DNA from a mouthwash containing cheek cells, or using kiwi fruit as a source of tissue.
Origami DNA
Having extracted DNA, students create a simple model of the structure of DNA using this origami activity, demonstrating its double helix structure.
I'm a Worm Get Me Out of Here
To investigate the variation between species, this cheap but effective activity looks at how colour of worms can affect their chances of survival and provides a simple model for natural selection.
The procedure uses different coloured baits (‘worms’) that are selected and eaten by birds. Uneaten ‘worms’ are counted after predation and the ‘worm’ population is replenished in proportion to those colours which remain. After several cycles of predation and ‘breeding’, the proportions of the colours in the population change, simulating directional selection.
It is better to carry out the investigation between December and March, when wild food is scarce and birds will be more likely to take food that is put out for them. The RSPB Pocket Guide to British Birds and the Key to Identifying Common Birds will help to identify the birds.
Soil and Earthworm Survey - Which Earthworms Are Living in Your Local Area?
This is a great activity for developing an understanding of variation between species and changes in the environment can affect the population of different species.
Students should learn that changes in the environment may leave individuals within a species, and some entire species, less well adapted to compete successfully and reproduce, which in turn may lead to extinction. This resource also looks at the importance of biodiversity.
There are 26 different species of earthworms in Britain. Some are common and found in lots of places whilst others are increasingly rare. Earthworms are sensitive to many environmental factors, and these will influence where they live.
The exciting aspect of this resource is that students can compare their results with national statistics collected from other students at http://www.opalexplorenature.org/soilsurvey.
Explore, Discover, Inspire: Practical Work in Science
There is a surprising amount of biodiversity in the school grounds - even on the playing fields which look dominated by grass.
This activity can be used to develop an understanding of plant biodiversity and introduce the core fieldwork technique of random sampling with quadrats. Random sampling allows you to make an estimate of the populations of different species in any area, and eliminates sampling bias which can be introduced by the sampler selecting areas that look interesting or easier to count.
The Field Studies Council key Playing field plants is useful for identifying the species which typically would be found on a school playing field.
There is scope for students to develop and investigate hypotheses about plant distribution based on observations and measurements of factors such as soil, moisture, light intensity and wind speed. Observations of human or other animal activity in the area, and background information about the characteristics of common playing field plants, provide further starting points for developing hypotheses to test over short or long time scales.
