Ap Biology Research Paper

1) Plants have evolved many ways in which they can survive well on land.

a) Identify three changes that had to occur for plants to move from a life mostly in water to a life on land.

Three changes that had to occur for the plants to move from aquatic to terrestrial life are the following:

Body support: In water, the plants are buoyant and the effect of gravity on them is minimal. The reason of developing rigid stem is to support the plants in a way that it can grow higher above the land. Further, in order to absorb water and other nutrients from the soil the roots were developed to anchor the plant to achieve this purpose.

Material transportation: In the water, different parts of the plant get nutrients and water directly from their environment,

They are the most diverse and widespread division of spore-producing plants as:

• They have vascular tissues for the transportation of water and nutrients

• They do not produce flowers or seeds and reproduce through spores and its sporophyte has rhizomes, stem, and leaves

b) In as simple words as possible, describe the life cycle of a typical pteridophyte (fern).

In ferns, the dominant generation is sporophyte. The sporophyte is photosynthetic and is separated from the gametophyte. The haploid spores are produced in a sporangium. Each spore divides mitotically to produce a heart-shaped gametophyte. Male and female parts are developed on the same plant. Gametophyte is small in size and can photosynthesize. In order for the fertilization to take place, enough water should be available so that the sperm may swim to archegonia and fertilize the eggs. The sporophyte has vascular tissue and roots; the gametophyte does not.

9) Gymnosperms:

a) What makes gymnosperms especially suited for northern climates?

The gymnosperms are suited for the northern climates on the basis of following adaptations:

• They pyramidal shape of most gymnosperms allows snow and ice to slide off the strong

In pine tree, the sporophyte is the dominant generation. Pine produces two type of spores. Haploid pollen grains are produced in male cone. In a female cone, two ovules are present in every scale. One megaspore mother cell (megasporocyte) undergoes meiosis in each ovule. There is only one cell which is able to survive in total of four cell which then develops into a female gametophyte. The pollination occurs in female gametophyte. Fertilization occurs after successful pollination in which one sperm cell will meet with the egg and will make a diploid embryo which will be surrounded by seed coat of tissue from the parent