BIOL1030 Chap.11 Animal Reproduction, Development and Nutrition
Animal Reproduction, Development and Nutrition
Animal Reproduction, Development and Nutrition follows the Week 7 lectures on how a fertilised egg becomes a complex, working animal. It begins with the hormone relay from hypothalamus to pituitary to gonad, the feedback that steadies it, and how temperature can switch breeding on and off in ectotherms.
It then covers reproduction without males, the extraembryonic membranes of the amniote egg, cleavage and tissue-specific gene control. The last part is energy and food: ATP and ion pumps, how metabolic rate is measured and why it scales with body mass to the three-quarter power, what makes a diet complete, how animals steer towards a nutrient target, and how the hypothalamus balances hunger and satiety.
What this chapter covers
- 01
GnRH, LH, FSH and the male gonadal axis
- 02
Parthenogenesis, gynogenesis and how to tell them apart
- 03
Extraembryonic membranes, cleavage and tissue-specific enhancers
- 04
ATP, the sodium-potassium pump and metabolic rate
- 05
Body size scaling, BMR and SMR
- 06
Essential nutrients and nutritional geometry
- 07
Hunger and satiety hormones
Worked example · free
Compare metabolic demand in a 30 g and a 30 kg marsupial
- 1The mass ratio is 30 kg divided by 0.03 kg, which is 1,000.
- 1Total metabolic rate scales as mass to the 0.75, so the kangaroo's total rate is 1,000 to the 0.75, about 178 times the mouse's.
- 1Rate per gram scales as mass to the minus 0.25, so each gram of mouse uses 1,000 to the 0.25, about 5.6 times more energy than a gram of kangaroo.
- 1Feeding by the same energy per kilogram would therefore underfeed the mouse and overfeed the kangaroo.
Key terms
- Gonadotropin
- A pituitary hormone, LH or FSH, that acts on the gonads to drive steroid and gamete production.
- Parthenogenesis
- Development of an embryo from an unfertilised egg, so offspring carry only maternal DNA.
- Allantois
- The extraembryonic membrane that stores nitrogenous waste and supplies vessels to the chorioallantoic membrane.
- Basal metabolic rate
- The metabolic rate of a fasted, resting endotherm within its thermoneutral zone.
- Essential amino acid
- An amino acid the animal cannot make and must obtain from its diet.
- Nutritional rail
- The line on a protein-carbohydrate graph along which intake moves when an animal eats a single food.
Animal Reproduction, Development and Nutrition FAQ
Why does low testosterone not always raise fertility back to normal through feedback?
Low testosterone weakens negative feedback on the hypothalamus and pituitary, which normally pushes GnRH and LH upward. If the fault sits at the top of the axis, for example a chemical that suppresses GnRH, that upward push never happens, so sperm production stays low despite the weakened brake.
How can you tell parthenogenesis from gynogenesis?
In both, offspring carry only maternal DNA, so genotyping alone cannot separate them. Gynogenesis needs sperm to activate the egg while contributing no genes, so a controlled cross with genetically distinct sperm, followed by checking offspring for any paternal alleles and confirming egg activation, distinguishes the two modes.
Why do small mammals need more food per gram than large ones?
Whole-animal metabolic rate rises with body mass to about the three-quarter power, so rate per gram falls as animals get bigger. A tiny mammal also loses heat quickly, so each gram of its tissue demands far more energy, faster breathing and faster oxygen delivery than a gram of a large mammal.
Can a diet provide enough calories and still be deficient?
Yes. Calories only measure energy, while growth, repair and normal membranes need essential amino acids, essential fatty acids, vitamins and minerals that the animal cannot make. Adding more carbohydrate fixes none of these, so the gap shows up as slow growth or poor healing.
Exam move
Draw the gonadal axis from memory with every feedback arrow, then practise breaking it at a different level each time and predicting LH, FSH, testosterone and sperm output. For development, make a four-row table of the extraembryonic membranes with the defect each would produce. For energy, rehearse the scaling rule with two masses you choose, writing total and per-gram ratios separately.
Finish with nutrition: for any incomplete diet scenario, list the missing nutrient classes and a calorie-matched supplement experiment, and use the model answers from the week's practice questions to check the measurements you propose.
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