联系我们Ⅰ.Teaching Goals:
1.Talk about modern agriculture and the effects it has on people's life.
2.Practise giving advice and making decisions.
3.Use “It” for emphasis.
4.Read statistical graphs.
5.Write a plan for a vegetable garden.
Ⅱ.Teaching Time:
Five periods
Ⅲ.Background Information:
1.An American Small Farm
Last year,at harvest time,we visited the Steenhoek farm,which is 2 200 mu,or 340 acres.Typical family farms are run entirely by family members,with every member playing a vital part in the operation.Both of these families are descendants of Dutch immigrants who settled here over a century ago.
The Steenhoek farm supports 3 generations.The family of Mr.and Mrs.Steenhoek includes three children and 2 grandchildren.As we will see,this family is an excellent example of hardworking,eXPerienced farmers who stay on the land not purely because of profit,but because they are living a life-style that satisfies them.Sixty percent of the Steenhoek's acres are devoted to pasture land,on which they raise 120 beef cattle.The rest of the land is used for growing corn.
Fifteen years ago,the American farm economy was booming.Farmers could specialize,raising one crop,or one type of animal.Today,with an uncertain farm economy,such an idea is considered foolhardy,and diversifying is one way that farmers can lesson their risk of loss.For example,if weather affects the size of a crop,the sale of the livestock will make up the difference.If the animals are plagued by disease,at least there is grain to take to market.
Kendall Steenhoek,Simon's eldest son,divides his time between running this machine shop and farming zoo acres of corn.He attended a community college in Iowa for two years to study diesel mechanics.Then he opened this repair shop for farm machinery.Kendall also plants and harvests over 30 000 bushels of corn each year,but it is the income from the repair shop that has enabled him to stay within the farming community.The heavy equipment used on the farms today is in constant need of maintenance,and requires precision tooling for repairs.By far,the most impressive and certainly the most costly piece of farm equipment used on a small farm is a harvesting machine called a combine,which can cost up to $100 000.
This type of machinery is what makes the American farm so efficient.With a combine,one man and his family can harvest an entire crop of a 500 acre farm in two weeks.The value of the combine is that it performs several functions.As it moves through a field of corn,this sophisticated machine cuts the stalk,plucks the ear,discards the stalk,shucks the corn kernels off the ear and deposites the kernels in a storage bin in the back.Then,a spinning device in the rear of the combine shreds the husks and shafts and scatters them across the field,to serve as mulch,cutting down on the possibility of soil erosion from winter rains.The machine is even more amazing when you think that it has been in use on American farms for only one generation.
2.Genes
Every living cell contains genes.They are too small to be seen in a microscope,but they are vitally important.Each set of genes in the body contains all the instructions needed to make a human being.Some genes determine hair color.Some determine the shape of a nose.Some genes help determine your height and even your weight.
Genes are made of a chemical called DNA—the letters stand for deoxyribonucleicacid(脱氧核糖核酸).In the early 1950's,two scientists,Francis Crick and James Watson,figured out how the parts of DNA fit together.Once scientists understood this structure,it became possible to take pieces of DNA apart and put them together in new ways.New kinds of genes could be made in this manner.
Scientists have studied the genes of many plants and animals.They have worked out which genes affect the color of a tomato and the stickness of its skin.Working out which genes determine which features is called genetic mapping,scientists have begun the Human Genome Project,an ambitious effort to map
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人教版高一Unit 19 Modern agriculture