Natural Selection Homework assignment (10 points) Due next class period Students

Question

Natural Selection Homework assignment (10 points)

Due next class period

Students are to do this assignment independently

For one of the examples given below, explain how natural selection may have led to the evolution of the trait by answering these 5 questions. Type your homework, with answers numbered 1 - 5 and using complete sentences.

1) Identify the trait that you will describe and how that trait is beneficial to the species?

2) If you could go back in time and examine the ancestral species, would all of the organisms have looked identical? Describe the variation that may have existed within that ancestral species and which provided the ‘raw material’ for natural selection.

3) Why didn’t all of the offspring of these organisms survive? What type(s) of 'selective pressure' would have favored evolution of this trait?

4) Which organisms within the species would have been most reproductively successful? What does this mean?

5) How did the form of this trait change over time? Would you expect that the modern form of the trait evolved quickly with few intermediate steps, or slowly and gradually?

Explanation / Answer

Natural selection:

Natural selection refers to the process in which a certain species with an inheritable advantageous trait with respect to their environment will proliferate. Darwin proposed the natural selection theory as the main mechanism of evolution. Darwin’s finches are categorized as the emblems of evolution.   

Natural selection is commonly known as “survival of the fittest,” because it is a natural and unguided process. It states that traits, which are advantageous to an individual, will help that individual reproduce more successfully, and thus the population will keep traits that are advantageous.

Traits that do not help an individual will likely lead to that individual not reproducing and that trait not showing up in subsequent generations. Darwin’s finches are categorized as the emblems of evolution. Natural selection favors different varieties of species in different islands.

The theory was illustrated by exemplifying different varieties of finches, living in the Galapagos Island. The finches were of various types: seed-eating finches, cactus-eating finches, and insect-eating finches. The finches more or less resembled each other, but developed different mouth structures based on their food habits.

Natural selection depends on several factors, like

For example, consider green grasshoppers versus brown grasshoppers.

1)

The selected trait is camouflage:

Grasshoppers have the tendency to change colors (camouflage). So, based on the environmental conditions, the green grasshoppers change their color into brown to escape from natural predators. It results increase change of survival of green grasshoppers, however they still have less chance of differential reproduction.

2)

No, all the ancestral species do not look identical, due to sexual dimorphism. Sexual dimorphism is the physical character based difference between male and female of the similar species. The difference is based on presence and absence of reproductive organs. This may increase speciation rate due to sexual selection of secondary sex traits.

Charles Darwin stated that the sexual selection is depends on the variation of the size of eggs and sperm. The smaller sperms are active, which compete for fertilization with larger eggs and gives male with larger body size and females with small body size. However, in certain species females have more body mass of size than males, irrespective of gametes.

3)

Due to drought conditions or changes in the natural environment, green grasshoppers do not get enough food. Invading of birds is also a natural threat. Thus, the lack of food and presence of threat will decrease the overproduction green grasshoppers. The population of green grasshoppers is becoming more stable with brown grasshoppers.

4)

Due to drought conditions and lack of food, both green and brown grasshoppers will compete for food, and thus survival. However, the brown grasshoppers have more chance survival, because they do not have any natural threat.

5)

As brown grasshoppers as best adapted to the drought conditions, they will have more differential reproduction capability than green grass hoppers. Therefore, their trait change over time and the modern form of the trait evolved gradually.   

Related Questions

Navigate

• Browse (All)
• Browse N
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.