Sexual Reproduction In Animals
Asexual Reproduction Animals and Plant Sexual Reproduction in plants
Reproduction : defined as a biological process in which an organism gives rise to offspring to itself.the ability to produce offspring or new individual of the same species through a sexual or asexual process is a fundamental feature of all known life. A new individual normally goes through a period of growth and development before it reaches a stage when it can reproduce.
Reproduction basically divided in to two types , 1. asexual reproduction.2.Sexual reproduction,
Asexual Reproduction : is a process in which the organism reproduce on its own without the help of another individual. There is only single parent. Asexual reproduction occurs in all prokaryotes and some of eukaryote . Cell division is mitosis .
Sexual Reproduction: is a process in which two parents ,male and female are needed to produce new one .Cell division is generally meiosis . Depends up on this type of division we get gamete having half the number of parent chromosome. That is join with other parent half number chromosome gamete , produces zygote which is have original number of chromosomes.
Mitosis division :
Here two important divisions
first nucleus divides in to two identical set of genetic material.
Then cytoplasm divide, this process is called cytokinesis.
Prophase , metaphase, anaphase, telophase .
Here chromosomes number is same as with parent cell.
pro-phase: Chromosomes are appear ,chromosomes become double by the replication .
Nuclear envelop will disappear.
The mitotic spindle forms.
Spindle fibers from each centriole attach to each sister chromatid at the kinetochore
Metaphase:observe thick chromatin structure are lined up on center of the cell ,which are attaches with spindle fibers which pulls towards poles.
Anaphase : Spindle fibrous which attaches to the chromatid ,became shorten .they separate chromosomes in to sister chromatids. this shorten spindle fibrous pulls sister chromatid towards poles.
Telophase: chromosomes became decondense .
Nuclear envelop forms and cytokinesis start .
Meiosis cell division : two phase are there. meiosis 1 and meiosis 2 .
Meiosis 1 : diploid cell became haploid cell ,form two number of cells
Meiosis 2: Mitotic division ,here from two haploid daughter cell become four daughter cells.
Meiosis 1:
prophase: Chromosomes became tetrads by synapsis of the homologous chromosomes. Crossing-over between homologous chromosomes produces chromosomes with new associations of genes and alleles.The occurrence of a crossing-over is indicated by a special structure, a chiasma.
Metaphase:Chromosomes alinement take place .
Anaphase:
Homologous chromosomes separated and sister chromatids remains together.
Telophase: Telophase I is similar to Telophase of mitosis, except that only one set of (replicated) chromosomes is in each "cell". Depending on species, new nuclear envelopes may or may not form. Some animal cells may have division of the centrioles during this phase.
meiosis phase 2 is exactly like mitosis. after meiosis 2 division 4 haploid daughter cells are form.
