Question

In what way was the seed an important adaptation in the evolution of plants? Explain the difference between pollination and fertilization. How much time elapses between these two processes in pine? 1. 2. 3. Outline the main events of the pine life cycle. Where are the gametes produced? Where are the spores produced? What generations are independent? At what stage does dispersal occur? Make a table like the one below where you compare reproduction, dispersal, and protection of the zygote or embryo. Your table should include things such as the mode (water, air, etc) and the structure involved (e.g. pollen, archegonia, etc) 4.

Answer 1

ANSWER 1

Formation of seed is an important adaptation for the land.

The evolution of seed allowed plants to to decrease their dependency upon water for reproduction.

It is needed that the seed remain dormant for a long period because condition is not favorable all the time .So soil plays an important role in evolution.

Pollination is important aspect seed can be dispersed far and wide by many ways such as wind ,bird ,animal etc.Thus increasing the chances of finding good conditions.The protection is enhanced by seed coat.

ANSWER 2

Pollination is a process of transferring pollen from one flower to another while fertilization occur after successful transfer of pollination .In Fertilization fusion of male and female gamete occurs in plant.

Another difference is ,only flowering plant gone through  the process of pollination,where as fertilization is common in all living organism.

In pollination ,medium like wind,animal,is required while in fertilization there is no medium is required.

Pollination is external mechanism while fertilization is internal mechanism.

In pine fertilization occurs 15 minutes after pollination.

ANSWER 3

Pine trees are conifers carry both male and female sporophyll on same mature sporophyte.Pine generating two different type of spores male microspores and female megaspores .

In the male cone the microsporocytes give rise to pollen grains by meiosis ,in the spring season pollen are released and carried by wind.Some gametophyte will land on female cone.The pollen tube develop slowly as the generative cell in the pollen grain divides into two haploid cell by mitosis.

when mature each microspore germinates means cell division starts.

pollen cones are formed ,female cone form near the tip of branches.At the time of pollination scales are separated to allow pollen to fall between them to reach the ovules.

Each fertile scale has 2 ovules on its upper surface.

Ovule consist of a sporangium ,at the center of it a special cell called sporocyte,divideds into 4 haploid spores by meiosis

Megaspore now germinates to form gametophyte.one of the cell inside pollengrain divides into 2 sperm cell which travel along pollen tube to reach an egg.

Zygote formation and zygote divides into several nuclei.they are arranged themselves into 4 tier of 4 cells.

The end tier become 4 embryo cell,as the 4 embryo cell are pushed deeper into the gametophyte they split apart into 4 seperate suspensors.The 4 embryo generate and become multicellular.

Surviving embryo enlarges as it form root tip,shoot tip and several seed leaves.

ovules have been developing into seed the entire female cone has become large and woody.