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as a child's overall size increases, different parts of the body grows at different rates. Discuss the two growth patterns that describe these changes. Describe the two types of brain development and give examples of appropriate stimulation for each. (the answer must be a two page double spaced paper).

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Patrina SchowalterLv2
13 Dec 2019
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Related questions

QUESTION SET 3

Sexual Selection, Developmental Thresholds, and Ornamentation

INTRODUCTION

In Chapter 10 you read about how sexual selection can drive the evolution of bizarre and sometimes costly ornamentation or weaponry in animals, often in males. This paper reveals a situation where sexual selection is the driver, but the result is more complex than might be expected at first glance. The authors describe some beetle species where different thresholds encountered as larvae result in different levels of ornamentation, and consequently different reproductive strategies.

The authors show that in one family of beetles (the Scarabeidae [dung beetles]), two different threshold mechanisms have independently evolved. Each of these thresholds has a different effect on horn development in the males of these beetles. Both mechanisms are triggered by body size in larvae. For one mechanism, if a larva attains the threshold size its adult morphology (the phenotype it will have after it pupates) switches from being hornless to being horned. The second threshold, also based on larval body size, similarly results in either having a short or a long horn (see Figure 2).

This discovery led the authors to look more closely at other beetle species where male polymorphism was known to occur, and they found two other examples where this double threshold mechanism was operating (see Figure 1). In the family Lucanidae (stag beetles), they found that male trimorphism was characterized by differences in the mandibles, with male mandibles exhibiting three increasing sizes moderated by the thresholds. In the family Curculionidae (weevils), the thresholds controlled the development of ventral body spines. Here, the beetles either lacked spines (and thus resembled females), had short spines, or had long spines.

The authors suggest that this multiple-threshold system may be more prevalent than previously thought, and anticipate more examples coming to light.

QUESTIONS

Question 1

What are polyphenic regulatory developmental mechanisms?

Answer:

Question 2

Can you think of an example of polyphenic regulatory developmental mechanisms besides the beetles mentioned in this paper.

Answer:

Question 3

The authors use the “rock-paper-scissors” analogy to describe the potential result of this two threshold system when it comes to reproductive success in dung beetles. As in the game of rock-paper-scissors, each possible pair-wise comparison has a clearly defined winner. Give a hypothetical example of what this might look like in the context of dung beetle mating success.

Answer:

Question 4

What is the difference between the systems described in this paper and the other examples of male trimorphism cited by the authors (in isopods, lizards, and birds)?

Answer:

Question 5

Why might a trimorphic system such as this evolve? Why wouldn’t natural selection just drive all males to have the biggest possible horn, spine, or whatever the ornament involved is?

Answer:

1. What is an organic molecule?

2.Name three hydrocarbons and be able to draw their structural formulas.

3. What is an isomer? List and describe the three types (structural, geometric, and enantiomers).

4. Be able to recognize and describe the properties of these functional groups: aldehyde, ketone, hydroxyl, sulfhydryl, carboxyl, amino, and phosphate groups.

5. What is a monosaccharide? Give two examples of these molecules and their functions.

6. Describe these chemical reactions: dehydration synthesis (condensation reaction) and hydrolysis (rehydration).

7. What is a disaccharide? List two and give their functions.

8. What is a polysaccharide? List two storage forms and two structural forms. How are they formed and what is their specific function?

9. How do the pancreatic hormones insulin and glucagon regulate blood sugar levels?

10. What is molting and why is it necessary in certain animals?

11. What four molecules are bonded together to form a triglyceride or fat? Why are fats nonpolar? What are some functions of fats as well as other lipids such as oils and waxes?

12. How do saturated and unsaturated fats differ? Discuss bonding patterns and possible sources of these fats. Which type is healthier for you? Why?

13. Why do animals store most of their excess glucose as fats or oils rather than as glycogen or protein? Give two reasons.

14. What are phospholipids? Identify parts of the phospholipid bilayer that are hydrophobic or hydrophilic? What important cell structure do these molecules help create?

15. Describe the structure of a steroid. How is cholesterol used in beneficial ways in your body?

16. What are LDLs and HDLs? Which is considered good or bad cholesterol? What condition could result from high blood pressure?

17. What are four ways to either reduce high blood cholesterol or maintain a safe level?

18. What is the composition of an amino acid? Why would they be considered nonpolar, polar, acidic, or basic?

19. Define dipeptides and polypeptides.

20. Describe the primary structure of a protein. What type of bonding creates it?

21. What is the secondary structure of a protein? Name two types of secondary structure and indicate what type of bonding holds them together. List three fibrous proteins.

22. What is the tertiary structure of a protein? What types of bonds or chemical interactions allow a protein to maintain this structure? List three globular proteins.

23. What is the quaternary structure of a protein? Describe a hemoglobin molecule.

24. What are the subunits of nucleic acids and what is their composition? How are these subunits bonded together? What is DNS's basic shape?

25. List three differences between DNA and RNA.

As an animal’s body size increases, the number of cells in the organism also increases. Why must the number of cells increase in order to increase body size? Why can’t there simply be the same number of cells, each with larger volume?

All animals begin life as a single-celled zygote, but become multicellular through development. The increase in number of cells must come from an increased number of mitotic divisions and this in turn may increase the risk of developing cancer. However, when looking at animals of varying body size, scientists find no correlation between body size and cancer incidence. In fact, some large bodied animals such as elephants (Loxodonta africana and Elephas maxima) have very low rates of cancer. It has recently been reported that elephants have at least 20 copies of the TP53 gene that makes the protein p53, whereas humans only have one copy (2 alleles).

Describe the process whereby elephants probably acquired so many copies of the TP53 gene? Hint: it also may have been responsible for so many copies of CYP, RAS and BRC1 genes.

How is the possession of extra TP53 genes and adaptation for large, long-lived organisms? In your answer, identify which cancer hallmark this may be an adaptation against.

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