Teaching objectives of lecture notes on biological evolution in senior two;
1. Explain the main contents of modern biological evolution.
2. Summarize the theory of biological evolution and the formation of biodiversity.
Teaching emphases and difficulties:
1. Discuss the change of population gene frequency by mathematical method.
2. Explain some biological phenomena from the viewpoint of biological evolution.
Autonomous learning and key explanation;
First of all, Lamarck's theory of evolution
Lamarck: French naturalist who was the first to put forward a relatively complete theory of evolution.
1. Viewpoint: All living things on the earth were not created by God; It is gradually evolved from lower level to higher level by older creatures; The formation of various adaptive characteristics is due to use, rejection and acquired inheritance.
2. The progressiveness of Lamarckian evolutionary theory: opposing creationism and species invariance.
Limitation: almost deny the real existence of species, and think that there are only individuals with continuous variation in biology.
Most theories come from subjective speculation.
Second, Darwin's theory of natural selection.
Fact 1: All living things have a tendency to _ _ overproduce.
Fact 2: The number of individuals in a species can remain stable. Inference 1: struggle for existence exists between individuals.
Fact 3: Limited resources Fact 4: There are wide differences among individuals.
Fact 5: Many variations are heritable.
Inference 2: individuals with favorable variation, inference 3: _ _ favorable variation accumulates from generation to generation,
The chance to survive and leave future generations. Many creatures are constantly evolving into new types.
1. The main contents of Darwin's natural selection theory summarized from the above deductive model are: over-breeding; Survival competition, genetic variation, natural selection.
2. The progressiveness of the theory of natural selection: it makes biology get rid of the shackles of theology for the first time and embark on the scientific track; It reveals that the unity of life phenomena is due to the fact that all living things have the same ancestor. Biodiversity is the result of evolution; There are certain internal relations among various species in the biological world, which promotes the development of various branches of biology.
3. Limitation: Limited by the level of scientific development at that time, it is impossible to scientifically explain the nature of _ genetic variation. Secondly, it pays attention to the evolutionary value of individuals and ignores the role of groups.
Third, the development of evolution after Darwin.
With the development of science, the research on heredity and variation has developed from trait level to molecular level, and the research on natural selection has also developed from individual to population as the basic unit. In this way, a modern biological evolution theory with natural selection as the core has been formed.
Fourth, modern biological evolution theory.
(A) population is the basic unit of biological evolution
1, population
(1) Concept: All individuals of the same species living in a certain area.
(2) Features: Non-mechanical assembly. Individuals can mate with each other and pass on genes to their offspring through reproduction. So population is also the basic unit of biological reproduction.
2. Gene bank: All genes contained by all individuals in the population.
3. Gene frequency: the ratio of one gene to all alleles in a population gene pool.
Example 1. A classmate calculated an example: 100 individuals were randomly selected from the population of an organism, and the genotypes of 20 individuals were aa, Aa and AA respectively. How often does a gene appear in (1)? (2) What is the frequency of a gene?
A gene frequency = _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
A gene frequency = _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
According to separation of mendelian law:
Frequency of parental genotype AA(20%) Aa(60%) aa(20%)
The ratio of gamete A() a ()
The genotype frequency of offspring AA() Aa() aa ()
Offspring gene frequency A() a ()
The second generation AA() Aa() aa () genotype frequency
The second generation gene frequency A() a ()
(3) When a new allele A2 is produced, will the gene frequency of the population change? How will the frequency of gene A2 change? .
(2) Mutation and gene recombination provide raw materials for biological evolution.
1, variation type
2. Under natural conditions, the frequency of variation is very low, and most of them are harmful. Is it significant for biological evolution?
For example, each fruit fly has about 104 pairs of genes, assuming that the mutation rate of each gene is 10-5. If the population of Drosophila is moderate (about 108 individuals), please calculate the number of gene mutations in each generation. The number of gene mutations is 2? 107。 This shows that the number of gene mutations produced by each generation of the population is very large, which is accumulated through reproduction and becomes the basis of gene frequency change. Moreover, the advantages or disadvantages of mutation are not absolute, depending on the living environment of organisms.
3. Is there a direction for mutation and gene recombination?
Because mutation and gene recombination are random and directionless, they only provide raw materials for biological evolution and cannot determine the direction of biological evolution.
(3) Natural selection determines the direction of biological evolution: under the action of natural selection, the gene frequency of the population will change directionally, leading to the continuous evolution of organisms in a certain direction.
Answer:
Example1.50%; 50%
Frequency of parental genotype AA(20%) Aa(60%) aa(20%)
Gamete ratio A( 50%) a( 50%)
The genotype frequency of offspring is AA( 25%) Aa(50%) aa( 25%).
Offspring gene frequency A( 50%) a( 50%)
The genotype frequency of the second generation was AA( 25%) Aa( 50%) aa( 25%).
The frequency of the second generation gene is A( 50%) a( 50%).