Experiment Topics Inspired By Darwin

Dr Sue Johnson has since 2002 completed the research and written course material for teachers and pupils on six experiment topics inspired by Darwin's work at Downe.

Each topic summary (below) has an explanation extracted from the National Curriculum (England and Wales) to indicate how Darwin's work might be included in schools. Each topic summary also describes a link to Darwin's observations and writings (in italics).

Weeds - Plant Numbers Are Kept In Check
How predation and competition for resources affect population size. About food webs composed of several food chains, and how food chains can be quantified.

"But the real importance of a large number of eggs or seeds is to make up for much destruction at some period in life; and this period in the great majority of cases is an early one."

Worms Bring Subsoil To The Surface
The distribution of organisms depends on environmental factors; sustainability is affected by human activity; fauna, such as worms, act as environmental indicators.

Darwin tells us that the action of the worms caused his worm stone to sink at a rate of 2.2mm a year. He estimated that the action of earthworms on every acre of his land brought some 18 tons of soil to the surface annually.

A Tangled Bank
That habitats support a diversity of plants and animals which are interdependent.

"It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us."

Artificial Selection
That selective breeding can lead to new varieties. Human management of food production has environmental implications for animal and plant populations.

Darwin relates selective breeding of food plants to human survival. "We probably owe our knowledge of the uses of almost all plants to man having originally existed in a barbarous state, and having been often compelled by severe want to try as food almost everything which he could chew and swallow. Accustomed as we are to our excellent vegetables and luscious fruits, we can hardly persuade ourselves that the stringy roots of the wild carrot and parsnip, or the little shoots of the wild asparagus, or crabs, sloes, &c., should ever have been valued."

Natural Selection
Small inherited changes can assist individuals to survive.

"When we reflect that certain extraordinary peculiarities have thus appeared in a single individual out of many millions, all exposed in the same country to the same general conditions of life, and, again, that the same extraordinary peculiarity has sometimes appeared in individuals living under widely different conditions of life, we are driven to conclude that such peculiarities are not directly due to the action of the surrounding conditions, but to unknown laws acting on the organization or constitution of the individual."

Pollination
Variability is the raw material of evolution. Variation in plant species starts with exploration of how they are pollinated.

"Cross fertilisation is also ensured in many cases by mechanical contrivances of wonderful beauty, preventing the impregnation of the flowers by their own pollen." Seeing insects entering and leaving flowers filled Darwin with pleasure.