Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things...
-
Upload
sophia-merritt -
Category
Documents
-
view
218 -
download
1
Transcript of Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things...
![Page 1: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/1.jpg)
Cell Reproduction
![Page 2: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/2.jpg)
Need For Reproduction
Reproduction is the life process in which living things produce other living things of the same species.
Reproduction is not necessary for the life of one individual organism.
It is necessary for the continued survival of a particular group of organisms.
![Page 3: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/3.jpg)
Cell Division All cells arise from other cells by cell division. When cells grow to a certain size they must
either divide or die. If a cell continued to grow without dividing,
the surface area of the cell would become too small to hold the cell’s contents. (Problem of Surface Area/Volume Ratio)
![Page 4: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/4.jpg)
Mitosis Cell Division
Cell division is a complex series of changes in the nucleus of a cell that leads to the production of two new cells.
The new cells are called daughter cells. The nuclei of the daughter cells are identical to
each other and to that of the parent cell. The daughter cells grow and increase in size until
they divide and produce two more daughter cells. This process continues, resulting in organism
growth and reproduction.
![Page 5: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/5.jpg)
Mitosis All cells in the body (except sex cells) are produced
by the process of mitotic cell division. Mitosis involves a complex series of changes in
the nuclei of body cells that produce identical (same) daughter cells.
They have the same number and type of chromosomes as the parent cells. Primary purpose is to increase the number of cells
Daughter cells are genetically identical to the parents
Occurs during growth and asexual reproduction.
![Page 6: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/6.jpg)
The Cell Cycle – Stages of Mitosis
Although the events of mitosis are an ongoing process, they are generally described in terms of separate phases, or stages. Interphase Prophase Metaphase Anaphase Telophase
![Page 7: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/7.jpg)
Mitosis
![Page 8: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/8.jpg)
Interphase Interphase is the period
between cell divisions. During interphase, the
single-stranded chromosomes replicate (make an extra copy).
The chromosomes can not be seen during interphase.
Nucleus
Chromosomes
![Page 9: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/9.jpg)
Interphase
Interphase Sometimes called the
“resting stage” between divisions
BUT cells are metabolically very active
The amount of DNA in the nucleus doubles
New organelles such as mitochondria are made.
![Page 10: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/10.jpg)
Prophase In prophase, the double-
stranded chromosomes become visible, and the nuclear membrane disappears.
A spindle apparatus, consisting of fibers, forms between opposite poles of the cell.
Chromosomes
![Page 11: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/11.jpg)
Prophase
Prophase Protein microtubules
develop from each centriole forming spindle fibres.
(In plant cells there are no centrioles and the spindle forms independently)
![Page 12: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/12.jpg)
Prophase
Prophase Towards the end of
prophase each chromosome can be seen to consist of two chromatids held together by a centromere.
![Page 13: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/13.jpg)
Prophase
Prophase At the end of prophase
the nucleolus disappears and the nuclear envelope breaks down.
![Page 14: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/14.jpg)
Metaphase During metaphase, the chromosomes move toward
the middle of the cell and line up at the cell equator (midline).
Chromosomes
Centrioles
![Page 15: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/15.jpg)
Metaphase
Metaphase Chromosomes line up
on the equator of the spindle.
They attach themselves to the spindle by their centromere
![Page 16: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/16.jpg)
Anaphase During anaphase, the double-stranded chromosome
separates and move to opposite poles of the cell. There is a complete set of chromosomes at each pole
of the cell.
ChromosomesCentrioles
![Page 17: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/17.jpg)
MITOSIS
Anaphase This movement results
from the contraction of the spindle fibres.
As they shorten they pull the chromatids apart.
![Page 18: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/18.jpg)
Anaphase
Anaphase The centromeres divide The free chromatids
move to the poles
![Page 19: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/19.jpg)
Telophase and Cytoplasmic Division
The last stage of mitosis is telophase. In telophase, a nuclear membrane forms around each
set of chromosomes, forming two identical nuclei. At the end of mitosis,
the cytoplasm divides, forming two new identical daughter cells.
![Page 20: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/20.jpg)
Telophase
Telophase The chromatids have
reached the poles and are now regarded as distinct chromosomes again.
A nuclear envelope forms around each group of chromosomes
![Page 21: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/21.jpg)
Telophase
Telophase The chromosomes
uncoil returning to chromatin
The cytoplasm divides by cytokinesis.
![Page 22: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/22.jpg)
CYTOKINESIS
Animal cells The centre of the cell
‘pinches in’ to form a division furrow.
As the division deepens, the cell surface membrane on each side joins up.
Two separate cells result.
![Page 23: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/23.jpg)
CYTOKINESIS
Plant cells Vesicles produced by the Golgi body collect
on equator of cell These vesicles fuse to form a cell plate. The cell plate eventually stretches right
across the cell forming the middle lamella. Cellulose builds up on lamella to form cell
walls.
![Page 24: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/24.jpg)
CYTOKINESIS
![Page 25: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/25.jpg)
The Cell Cycle
![Page 26: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/26.jpg)
Meiosis The process of meiosis involves two cell
divisions and produces cells that are different from the parent cell. Meiosis produces cells that have one-half the
number of chromosomes as the parent cells. If meiosis did not take place, the fertilized egg would
have double the amount of chromosomes it needs. Meiosis takes place during sexual reproduction
when sex cells, called the egg and sperm, are produced in sex organs.
![Page 27: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/27.jpg)
Meiosis One-half the number of chromosomes is called
the hapolid, (or n) number. In humans, the haploid number (n) is 23.
When the egg and sperm unite during fertilization, the species normal chromosome number called the diploid or (2n) number is restored (brought back). The diploid number in humans is 46. n (sperm) + n (egg) = 2n
![Page 28: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/28.jpg)
Meiosis
![Page 29: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/29.jpg)
Meiosis
Cell division that is vital for sexual reproduction
Takes place in reproductive organs
Results in formation of haploid gametes
The four daughter cells are not genetically identical
![Page 30: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/30.jpg)
Meiosis and genetic variation
There are two main ways in which genetic
variation occurs at meiosis:
1. Random segregation of chromosomes
2. Crossing over
![Page 31: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/31.jpg)
Meiosis and genetic variation
Random segregation During metaphase 1
homologous chromosomes arrive at the equator
They arrange themselves in a random order on the equator
![Page 32: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/32.jpg)
Meiosis and genetic variation
Random segregation In a cell with just two
pairs of chromosomes there are four different types of outcomes for the way the chromosomes can separate.
![Page 33: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/33.jpg)
Meiosis and genetic variation
Random segregation In human cells with 23
chromosomes there are 223 different possible ways the chromosomes can segregate!
That is over 8 000 000 different types of gamete
![Page 34: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/34.jpg)
Meiosis and genetic variation
During fertilisation any male gamete can join with any female gametes.
So thousands of millions of new genetic combinations are possible.
![Page 35: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/35.jpg)
Meiosis and genetic variation
Crossing over During prophase 1 of
meiosis homologous chromosomes come together in pairs
![Page 36: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/36.jpg)
Meiosis and genetic variation
Crossing over Each chromosome is divided into two
chromatids The homologous chromosomes twist around
each other This creates tension, which may cause
breaks to occur along the length of the chromatids
![Page 37: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/37.jpg)
Meiosis and genetic variation
Crossing over During cross over, corresponding fragments
may get swapped over. This “cutting and sticking” means that genetic
material is exchanged. This creates new genetic combinations and
variation in the gametes is increased.
![Page 38: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/38.jpg)
![Page 39: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/39.jpg)
Differences between mitosis and meiosis
Mitosis Meiosis
one division
![Page 40: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/40.jpg)
Differences between mitosis and meiosis
Mitosis Meiosis
one division two divisions
![Page 41: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/41.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes
remains the same
![Page 42: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/42.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes the number of
remains the same chromosomes is halved
![Page 43: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/43.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes the number of
remains the same chromosomes is halved
homologous chromosomes
do not pair up
![Page 44: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/44.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes the number of
remains the same chromosomes is halved
homologous chromosomes homologous chromosomes
do not pair up pair up to form bivalents
![Page 45: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/45.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes the number of
remains the same chromosomes is halved
homologous chromosomes homologous chromosomes
do not pair up pair up to form bivalents
chiasmata do not form and
cross over never occurs
![Page 46: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/46.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes the number of
remains the same chromosomes is halved
homologous chromosomes homologous chromosomes
do not pair up pair up to form bivalents
chiasmata do not form and chiasmata form and cross over
cross over never occurs occurs
![Page 47: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/47.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes the number of
remains the same chromosomes is halved
homologous chromosomes homologous chromosomes
do not pair up pair up to form bivalents
chiasmata do not form and chiasmata form and cross over
cross over never occurs occurs
daughter cells are genetically
identical
![Page 48: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/48.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisions
the number of chromosomes the number of
remains the same chromosomes is halved
homologous chromosomes homologous chromosomes
do not pair up pair up to form bivalents
chiasmata do not form and chiasmata form and cross over
cross over never occurs occurs
daughter cells are genetically daughter cells are genetically
identical different from the parent cells
![Page 49: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/49.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisionsthe number of chromosomes the number ofremains the same chromosomes is halvedhomologous chromosomes homologous chromosomesdo not pair up pair up to form bivalentschiasmata do not form and chiasmata form and cross overcross over never occurs occursdaughter cells are genetically daughter cells are geneticallyidentical different from the parent cellstwo daughter cells are formed
![Page 50: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/50.jpg)
Differences between mitosis and meiosis
Mitosis Meiosisone division two divisionsthe number of chromosomes the number ofremains the same chromosomes is halvedhomologous chromosomes homologous chromosomesdo not pair up pair up to form bivalentschiasmata do not form and chiasmata form and cross overcross over never occurs occursdaughter cells are genetically daughter cells are geneticallyidentical different from the parent cellstwo daughter cells are formed four daughter cells are
formed
![Page 51: Cell Reproduction. Need For Reproduction Reproduction is the life process in which living things produce other living things of the same species. Reproduction.](https://reader035.fdocuments.net/reader035/viewer/2022070403/56649f295503460f94c4220f/html5/thumbnails/51.jpg)
Comparison of Mitosis and Meiosis
Characteristic Mitosis MeiosisNumber of daughter cells 2 4
Number of cell division 1 2
Daughter cells are diploid or haploid
Diploid Haploid
Daughter cells are identical or different
Identical Different
Parent cell is diploid or haploid
Diploid Diploid