Sexual and Asexual Reproduction
Asexual reproduction is the formation of new individuals from the cells of a single parent , it is mostly common in plants more than animals. It is a biological process by which an organism creates a genetically similar copy of itself without the combination of genetic material with another organism.For example Hydra are able to reproduce by budding , sea anemones reproduce by binary fission, worms reproduce by fragmentation .
- Only one parent is needed.
- Very good chance of offspring would be created successfully.
- Takes a very short time .
- Fertilization is not necessary .
- They have identical characteristics of there parents.
- No chance of evolution taking place
- Since all genes are identical to parent , diseases , bad qualities are also passed down.
- They are all susceptible to the same disease.
Sexual reproduction means it involves the fusion of two special cells called gametes , one from a male source and one from a female source. is the making of new living organisms by combining genetic information from two individuals of diffrent sexes ( male and female ) . In both male and female sex cells ( sperms and eggs in animals , pollen and ovules in plants) are produced by a special cell division process witch halves the number of chromosomes in each resulting cell. The separation process of the chromosome makes sure that each sex cell has a unique combination of genes . In addition too asexual reproduction , sexual reproduction introduces variation into offspring , this is essential feature in order for evolution to take place .
- Two parents are involved.
- Fertilization takes place with combines genetic information.
- Large chance of unique organisms being created, therefore evolution taking place.
- The new organism formed has a chance of not getting its parents diseases passed to it.
- Only half the population is capable of genstation.
- There is no guarantee that the nucleus of the male sex cell would fuse with the female sex cell.
- Takes a good amount of time up.
- No guarantee offspring would be born.
Mitosis is the type of cell divison complete in 5 steps that result in two daughter cells each having the same number and kind of chromosomes as the parents nucleus ( basically means making an identical copy of itself ). The first step of mitosis is interphase . In this first step the DNA replicates itself in preparation for mitosis .The next step is Prophase , this is where the chromatin condenses into two rod shaped structures witch become the chromosomes , the third step is metaphase , in this step the cells chromosomes align them selfs in the centre of the cell , the fourth is anaphase , Witch replicates the chromosome and are split and daughter chromatins are moved to opposite poles of the cell .The last step of mitosis is telophase and cytokinesis in this step the sister chromatids reach opposite poles. The small nuclear vesicles in the cell begin to re-form around the group of chromosomes at each end and then the spindle fibres begin to disappear, two nuclei are formed and the cells divide.
Meiosis is a 10 step process where a single cell divides twice to produce four cells containing half the original amount of genetic information. These four daughter cells only have half the number of chromosomes of the parent cell. The first step in meiosis is interphase, the second is prophase l, the third stage is metaphase l, the fourth stage is anaphase l, the fifth stage in meiosis is telophase l, the sixth stage is prophase ll, the seventh stage is metaphase ll, next is anaphase ll, then telophase ll, and lastly cytokinesis. The real difference between mitosis and meiosis is that in the process of mitosis it only results in 2 organisms cells when in meiosis it results in 4 organism cells . Another difference between Meiosis and mitosis is that meiosis is a lot longer than mitosis, since it has more steps and more organism cells come out of it ex 4 instead of 2. Another thing is meiosis involves crossing over and in mitosis it does not involve crossing over, and the daughter cells in meiosis are not identical compared to mitosis where they are identical to the parent cell. Also the number of chromosomes in daughter cells produced by meiosis is half the number of chromosomes produced by mitosis.
Growth of organisms
Mating and Methods of Fertilization. Mating is the process by which gametes arrive in the same place at the same time . ( at which the female sperm cell and males meet at the same place ). Many animals have matting seasons that take place at certain times of the year to make sure that environmental conditions will be favourable for the development of their spring . In order for the cell to go through cell division there must be enough nutrients for the dividing embryo , temperature must be warm enough so proteins and enzymes will function properly during chemical reactions in development.
External Fertilization. Its a process called spawning a male fish to a female fish release there sperm cells+egg cells that meet outside there bodies. When the sperm cell meets the egg cell thats when the fertilization occurs. This process is normally common in species that are located under water.
Internal Fertilization. It is when sperm cells go into the females body and meet an egg cell.The sperm penetrates the egg and fetus starts to develop.The embryo develops and is nourished inside the mothers body.
Pollination .It is the transfer of pollen to a plant for fertilization .Pollen is a substance that is powdery , typically yellow, discharged from a male plant/cone. Fertilizing plants involving the fusion of male and female gametes.
Fetal Development.It is the stage that occurs before fetus begins to develop witch is also called embryonic development. Complete in 3 trimesters . First is developing organ systems , 8 weeks , 28g 9cm. Second is growth in fetus 12-16 weeks 650g 35cm.Third and last is continues growth of fetus 32 weeks 3300g 40-50cm.
An organism grows because cell division increases the number of cells in it, it is a process that takes place constantly. As the organism develops and its cells divide, most of them continue to divide. Even when they grow and develop it may look like it has stopped growing but it hasn’t, cell division is still occurring because they are losing cells also.
The longer it lives the bigger it will get because it just keeps increasing the number of cells using cell division. Then the new cells divide to create even more and it is just an endless chain of cell division, this is from mitosis.