Science Questions from page 59

Question 1a The fundamental cycle that allows all animals to reproduce sexually follows the same sequence: 1) meiosis produces gametes, 2) a male gamete combines with a female gamete, 3) a zygote is produced and develops into an embryo 4) the embryo develops through mitosis cell division into a mature offspring

Question 1 B This cycle ensures variation in offspring because meiosis allows for the exchanges of genetic material during crossing over in Prophase I. So, each of the daughter cells formed at the end of Telophase II have non-identical nuclei. As well, the haploid gametes combine to produce a diploid zygote. The zygote is unique because it contains genetic information from both parents.

Question 2A The function of mating is for two members of the same population to combine their gametes for fertilization. Mating alone does not ensure successful reproduction because the male may not be able to produce enough sperm, or enough viable sperm to fertilize the egg. Environmental conditions may not be suitable for bearing young. Sperm may never reach the eggs in external fertilization. The female may not be capable of maintaining the developing embryo for the entire gestation period in internal fertilization.

Question 2 B The function of fertilization is to unite the egg and sperm to form the zygote. Fertilization alone does not ensure successful reproduction because: zygotes could be eaten by a predator, the female may not be able to carry the zygote to full term.

Question 2 C Before reproduction can be considered successful, the resulting zygote must develop into an independent individual.

3a) The sea anemone probably releases more gametes at a time than a frog because sea anemones do not come together to mate. Releasing more gametes increases the chance that a sperm and egg will combine.

3b) Compared to whales, salmon would produce more offspring at a time. Salmon are external fertilizers; so the eggs must develop outside of the female’s body. Also, salmon do not protect their young once they hatch. Whales are internal fertilizers; have a long gestation period, grow to a large size, and require a lot of parental care. (Example, blue whales reproduce once every 2-3 years)

4) The requirements for successful fertilization are: Both males and female gametes arrives at the same place at the same time The zygote must receive enough food, moisture, warmth, and protection to develop

5) Neighbouring anemones release their gametes at roughly the same time, often responding to a cue in the environment (like a full moon). This increases the chance that sperm and egg will meet and unite. Also, anemones produce many gametes to increase the chance of successful fertilization.

6) Apply Newly hatched turtles might be less likely to survive than newly hatched birds because turtle parents provide no parental care. Many birds protect their offspring until they are ready to leave the nest.

7) Thinking Critically If the females frog is capable of dislodging a male before fertilization occurs, then this behaviour makes sure that only the strongest individuals are able to reproduce, so only the “best” genes are passed to the next generation.