1.4.4 Contrasting Lamarck and Darwin, Part II

Question 1

Lamarck’s theory for evolution

Answer 1

• was based on two ideas: use and disuse, and the

inheritance of acquired characteristics.

Question 2

Darwin’s theory of natural selection

Answer 2

• summed up by five main points: overpopulation, variation, competition, survival, and reproduction/inheritance.

Question 3

How would Lamarck have explained why woodpeckers peck at wood for food and have such good cushioning in their head?
How would Darwin have explained this?

Answer 3

• Lamarck would have said something like this:
  There were birds many years ago. Some saw bugs burrowing into the trunk of a tree. One of these birds would hammer its head into the tree to get at the bug. The bird kept on doing this until eventually its beak grew thick and its head became well cushioned. These traits were passed on to its offspring so that they too would have good cushioning and a nice thick beak.
• A Darwinian explanation would be something like this:
  A population of birds had grown quite large over time. Within this large population there were many slight variations. One strange bird could bang its head against the trees to get bugs. This trait happened to be a good variation for a bird to have because it helped the bird get food. The birds that couldn’t do this had to continue getting bugs from other places, but when the population is large it becomes harder and harder to find bugs in the obvious places. The head-banging bird was successful and survived; it reproduced and passed these traits on to its offspring. Among those offspring were still more variations. Some of these variants were more successful than others. The more successful ones were more likely to survive, reproduce, and pass their traits on to the next generation. Over a long period of time changes would accumulate, eventually giving rise to the woodpecker.

Question 4

selective pressure

Answer 4

• an outside force that affects the composition of a population by favoring certain traits over others

Question 5

Darwin’s theory of evolution was lacking

Answer 5

• an explanation for the source of variation of traits in a population.

Question 6

Darwin’s theory of natural selection includes the following ideas:

Answer 6

• overpopulation, variation of traits in individuals, competition, survival of the fittest, and reproduction.

Question 7

Natural selection may occur when

Answer 7

• there are differences in survival and reproduction among members of a population.
• more organisms are born than can survive.
• members of a population exhibit variation among heritable traits

Question 8

With which of the following ideas would Lamarck not agree?

Answer 8

• A purple-flower-loving cow is grazing in a field with purple and white flowers. The next year white flowers will dominate the population of flowers in the field.