Question

There are significant differences, as well as some similarities, in the life cycles of plants vs. animals.

a) Compare the general life cycle of a sexually reproducing plant vs. an animal.

b) Describe features that allow plants vs. animals to reproduce on land with a limited supply of water. Include both fertilization and subsequent development of the fertilized egg in your answer.
HINT: For plants, think of mosses which need a wet environment for reproduction as compared to flowering plants which can reproduce on dry land. For animals, compare an aquatic species to a bird or mammal.

Answer 1

(a) Comparison between life cycle of a sexually reproducing plant and an animal:

Plant life cycle	Animal life cycle
The juvenile phase is also called vegetative phase	No such specifications are there
The basic life cycle begibs from seed which grows, flowers, fruits and produce seeds of its own	Animals are either born from an egg (oviparous) or carried in womb (viviparous)
Thet are fertilized by external forces like wind, water, animals, etc	No external forces are required, they must copulate in order to reproduce
In their life cycle, the plants are most of the time sedentary	The opposite sexes are mobile individuals that interact physically with each other in mating process
The new plant is born by germinating from the seed	Animals life begins through exiting the mother's womb as an egg or newborn individual.
The prcocess of pollination iniitiates the fertilization process	Mating ensure the first step towards fertilization process
Spores are formed as method of dispersal in some plants	No formation of spores.

(b) The mosses require aquatic medium for gamete transfer but in flowering plants both the male and female gametes are non-motile. Here pollen grains are the carrier of male gametes and ovule has the egg. Presence of double fertilization is an unique event in case of angiosperms but is absent in bryophytes, pteridophytes and gymnosperms. Mosses and ferns produce a large number of male gametes because the chance factor to reach the female gametes is very faint, in order to compensate this loss they produce large number of male gametes. But in angiosperms generally two male gametes reach the ovule to ensure fertilization. Post fertilization produces structures like seed, flowers and fruits in flowering plants but in case of mosses, ferns and gymnosperms there is no such formation of this structures.

The aquatic species like fishes, amphibians have external fertilization whereas land animals like birds and mammals have internal fertilization. The medium of gamete transfer for aquatic species is generally water and gametes move towards each other by chemical stimulation. But in land plants the gamete transfer takes place by mating. Generally the aquatic species are oviparous but land plants like mammala are mostly viviparous with few exceptions.