Question

Explain the life cycle of angiosperms and gymnosperms ?

Answer 1

Angiosperms-During reproduction of flowering plants first spores are produced with half the number of chromosomes in their cell nuclei. The male spores lead to the formation of pollen grains in which the sperm cells arise. After fertilization a young embryo with again the same number of chromosomes as the parental plants develops in the ovule (more on fertilization in Angiosperms).                                                                                                                                                                                           GymnospermsMale and female cones develop on the mature sporophyte (the tree). Meiosis in the ovules of the female cones leads to the formation of female gametophytes, the embryo sacs containing each one egg. The male cone consists of scale that carry each a pollen sac in which pollen grains are produces through meiotic division. After bursting of the pollen sacs pollen grains are dispersed and can reach the female cone through the air. There a pollen tube can grow in which the sperm cells migrate tot the egg cell, ending in fertilization. An embryo is thus formed that ususally needs several years to develop into a complete seed that once on the soil will be able to germinate and to grow to a new sporophyte.         

Answer 2

Answer:

Y TAKEAWAYS

Key Points

Scientists classify fruit in many different categories that include descriptions, such as mature, fleshy, and dry; only a few are actually classified as being fleshy and sweet.

Some fruit are developed from ovaries, while others develop from the pericarp, from clusters of flowers, or from separate ovaries in a single flower.

Fruit are vital dispersal agents for plants; their unique shapes and features evolved to take advantage of specific dispersal modes.

Dispersal methods of seeds within fruit include wind, water, herbivores, and animal fur.

Key Terms

fruit: the seed-bearing part of a plant, often edible, colorful, and fragrant, produced from a floral ovary after fertilization

pericarp: the outermost layer, or skin, of a ripe fruit or ovary

hypanthium: the bowl-shaped part of a flower on which the sepals, petals, and stamens are borne

Fruit

In botany, a fertilized, fully-grown, and ripened ovary is a fruit. As the seed develops, the walls of the ovary in which it forms thicken and form the fruit, enlarging as the seeds grow. Many foods commonly-called vegetables are actually fruit. Eggplants, zucchini, string beans, and bell peppers are all technically fruit because they contain seeds and are derived from the thick ovary tissue. Acorns are nuts and winged, maple whirligigs (whose botanical name is samara) are also fruit. Botanists classify fruit into more than two dozen different categories, only a few of which are actually fleshy and sweet.

Mature fruit can be fleshy or dry. Fleshy fruit include the familiar berries, peaches, apples, grapes, and tomatoes. Rice, wheat, and nuts are examples of dry fruit. Another distinction is that not all fruits are derived from the ovary. For instance, strawberries are derived from the receptacle, while apples are derived from the pericarp, or hypanthium. Some fruits are derived from separate ovaries in a single flower, such as the raspberry. Other fruits, such as the pineapple, form from clusters of flowers. Additionally, some fruits, like watermelon and oranges, have rinds.

Regardless of how they are formed, fruits are an agent of seed dispersal. The variety of shapes and characteristics reflect the mode of dispersal, whether it be wind, water, or animals. Wind carries the light dry fruit of trees and dandelions. Water transports floating coconuts. Some fruits attract herbivores with color or perfume, or as food. Once eaten, tough, undigested seeds are dispersed through the herbivore’s feces. Other fruits have burs and hooks to cling to fur and hitch rides on animals