January 17

How do cells Multiply

Asexual reproduction is when the offspring is a genetic clone of the single parent. If the parent has a mutation the mutation is guaranteed to be passed down to the offspring. Some examples of animals that are able to create an offspring through asexual reproduction are cloning wasps, captive sharks, komodo dragons, whiptail lizards and marbled crab. In asexual reproduction their are four different methods for reproducing. They are Binary fission, fission, budding and Fragmentation. In asexual reproduction during the process of binary fission, genetic material (DNA) gets duplicated by an organism in the body. Later the DNA split into two parts, which is called cytokinesis. Binary fission is the primary of the reproduction process. Budding is another way of asexual reproduction. In some species, buds are able to be produced in almost any part of the body. Overtime the buds develop into an organism and duplicate the parent cell. Fragmentation is when a new organism grows from a fragment of the parent. All fragments eventually turn into a fully grown individual.

Sexual reproduction is When an offspring is created through a mix of two parents each with 23 chromosmes. The 46 chromosomes get passed down from the parents to the offspring creating the DNA for the child.  The offspring gets inherited genes from the parents with the process of fertilization. There are two types of fertilization, internal and external. For species that use internal fertilization the purpose is so the mother can protect the egg inside of her. The extra protection gives a better chance for the eggs survival because the mom will be supplying everything the egg needs. An example of species that produce internally are mammels. External fertilization occurs mostly in water or areas where it is very wet. When external fertilization occurs often multiple offspring are created. Sometimes the offspring will not make it into adult hood because there are risks for being fertilized in an outdoor climate. A couple of examples of species that produce externally are fish and amphibians.

Pro’s and Con’s of asexual and sexual reproduction.

Pros of sexual reproduction: With sexual reproduction there are two parents involved meaning the offspring will be unique and not exactly the same as either parents. Also the offspring has a chance in not receiving the same decease of the parent because the offspring is not a genetic clone of a single parent. Unlike asexual reproduction it is possible for a new species to be discovered during this process.

Cons of sexual reproduction: Only half the population (females) are able to reproduce and they must have a mate to do so. There has to be two parents to create an offspring and it takes nine months for the child to be born. Within those nine months something can happen to create a miss carriage and there is no guarantee that the baby will be born.

Pros of asexual reproduction: Only one parent is needed to create an offspring. There is a high chance that the offspring will be created successfully. Fertilization is not necessary and the offspring will be the exact same species and will have identical characteristics as its parent. Asexual reproduction includes fewer steps then sexual reproduction making it more reliable.

Cons of sexual reproduction: The offspring would be a genetic clone of its parent meaning the parents mutations or diseases will for sure be passed down to the offspring. There is almost no chance at all for evaluation taking place for the offspring. A disadvantage for plants using the vegetation method is that they are all likely to be effected by the same disease and they can be harmed by the same conditions.

 Meiosis is a form of cell division that produces useful cells such as sperm and egg cells, plant and fungal spores. All cells originate from other cells through a mechanism called cell division. The parent cell splits into two or more cells called daughter cells. Through cell division we are able to pass down genetic information from generation to generation. The daughter cells that meioses produces are only half of the amount a parent cell has. The mother and father chromosomes exchange bits to create  unique chromosomes for the daughter cell. The first step of meiosis starts with chromosomes duplicating. Then the cells go through two rounds of division with the final product of four daughters cells, each with half the amount of chromosomes from the parent cell.
In Meiosis I the sister chromatids blend together at the centromere and form the shape “X “, they become dense compacted structures that are now visible underneath a microscope. Prophase I sister chromatids from the mothers set of chromosomes
pair together with their identical protective chromosomes. The maternal and paternal chromatids exchange pieces of DNA and then recombine to new genetic variations. In a male human, even though the sex chromosomes (X and Y) are not alike they still exchange DNA and pair together. At the end of prophase I, the nuclear membrane breaks down. Metaphase I emerging from a structure called the centriole, meiotic fibres and a long chain of proteins are positioned at either end of the cell. The meiotic spindle hooks onto the fused sister chromatids. At the end of metaphase I, the sister chromatids are at their centromeres and line up in the middle of the cell. Anaphase I the spindle fibres start to separate, pulling sister chromatids with them. The X-shapped
chromosomes start to split and half of each chromosome ends up on opposite sides of the cell. Telophase I the sister chromatids reach the ends of the cell as it splits into two. The result of Meiosis I ends with two daughter cells with each containing a set of fused sister chromatids. The two daughter cells from Meiosis I transition in to Meiosis II where there is no more chromosomes being duplicated.
In Meioses II by the end of the process the number of chromosome will not have changed even though by the end of meiosis II there will be four daughter cells and not two. Prophase II meiotic spindles start to form again after the nuclear membrane starts to break apart. Metaphase II the  meiotic spindles hook onto the centromere of the sister chromatids and they all line up in the centre of the cell. Anaphase II the spindle fibres start to break away and sister chromatids are pulled apart. The individual chromosomes begin to separate on to each end of the cell. Telophase II once the chromosomes reach opposite ends of the cell the nuclear membrane forms again and the cell body splits into two. There are now four daughter cells each with the same amount of chromosomes in them. Every single one of the chromosomes are unique because they came from maternal and paternal chromosomes, originally from the parent cell.

Mitosis is similar to Meiosis where the organisms generate new cells through cell division. In this process, the parent cell will divide and produce an identical daughter cell. In Mitosis a cell isolates its duplicated DNA, finally dividing its nucleus into two. Mitosis is divided into four stages (P-MAT), these four stages are also seen in the second half of Meiosis.
Prophase the chromosomes that have been duplicated are combined and can be seen by the sister chromatids. The mitotic spindle and a narrow chain of protein moves to a structure called centrioles at either ends of the cell. Metaphase at the centromere after the nuclear membrane dissolves, the mitotic spindle hooks onto the sister chromatids. The mitotic spindle is now able to move the chromosomes in the cell. At the end of Metaphase all chromosomes are alined in the centre of the cell. Anaphase the mitotic spindle leaves and pulls the sister chromatids apart, leading them to move to opposite ends of the cell. Telophase the chromosomes go to either end of the cell, after cytokinesis occurs when the nuclear membrane reforms and the cell body splits into two. At the end of Mitosis, a cell produces a genetically identical daughter cell.
Mitosis and Meiosis compare and contrast
Compare: Mitosis and Meiosis both use the form of cell division and they both are used for reproducing. They both share many steps of their own process going through P-MAT. Meiosis and mitosis both produce new cells through dividing their parent cell and creating new daughter cells.
Contrast: The purpose of Mitosis is for asexual reproduction, growth and cell regeneration. At the end of the whole mitosis process it ends with a single nuclear division resulting with two nuclei that dived into two new daughter cells. Th nuclei from mitotic division from mitosis are genetically identical from the original nucleus. In mitosis the daughter cells have the same number of chromosomes as the parent cell.
The purpose of Meiosis is sexual reproduction and gametes. At the end of the entire meiosis process there are two nuclear divisions which leads to having four new daughter cells in the end. The nuclei from meiosis are not genetically identical because crossing over occurred and only the nuclei contain one set of chromosomes. In meiosis the daughter cells have half the amount of chromosomes the parent cell has.
 
 How organisms grow  
Matching + Methods of fertilization
The process of mating includes gametes. Gametes is a male or female germ cell that can be united with the opposite sex during sexual reproduction. For animals it is very different then from humans, many animals have matting seasons during certain times of the year to make sure the environmental conditions will be okay for their offspring. For humans we do not have a specific matting season because the weather conditions do not effect the offspring. The two main types of fertilization are internal where the sperm and egg unite inside the parents body, and external  where the sperm and egg unite outside of the parents bodies.  Sperm cells are deposited inside the females body were they meet an egg cell. The conditions that need to be met to be able to have the fertilized egg go through cell division are, there must be enough nutrients for the dividing embryo. For the proteins and enzymes to function properly during chemical reaction in developing embryo, the temperature must be warm enough. There must be sufficient moisture so the embryo does not dry out. Embryo must be protected from predators and from other environmental factors such as ultra violet radiation.
The Transfer From Pollen to Plant for Fertilization

Pollen is a substance that is powdery and typically yellow. It is discharged from a plant to a clone. Fertilizing plants involving the fission of male and female gametes. Pollen can be transferred by people, bees, butterflies, moths, flies, hummingbirds and wind. The embryo develops in the female part. A few disadvantages on how pollen is transferred are the birds are less immune to disease. The variability and hence adaptability to change the environment has been reduced.  New useful characters are not frequently being introduced. Some advantages on how pollen is transferred are self pollination eliminates some bad inactive characters. The plant does not need to produce large number of pollen grains. Flowers do not develop devices for attracting insect pollinators.

Embryonic Development

Embryonic  development is when the embryo begins to form and starts to develop. For humans, during the first two months after fertilization the embryonic development takes place. Once fertilization is over zygote begins the process of mitosis and a series of rapid cell division occurs. Embryonic development goes through four stages which are morula stage, the blastula stage, the gastrula stage and the neurula stage. The process of embryonic development is stem cells divide, migrate,and specialize. In the early stages of development, the inner cells mass start to form. The inner cells mass are the cells that produce tissues of the body. During gastrulation later in the development, the three germ layers form. After this stage it is common that most cells become more restricted in the types of cells they can produce.

 

Fetal Development

The stage that occurs before the fetus begins to develop is embryo development. In the first stage of the first trimester, organisms start to develop. The first trimester takes eight weeks of fertilizing the egg with the offspring to be about 28 grams and 9cm long. During the second trimester the offspring grows in the fetus for about 12-16 weeks with the weight of the offspring to be about 650g, and 35cm long. In the final trimester the growth of the fetus continues with the time of 32 weeks being fertilized. At this point the offspring is approximately 3300g and about 40-50cm long.

Internal fertilization  

 Internal fertilization is when the sperm and egg cells meet inside the female body. The fetus starts to develop when the sperm penetrates the egg. After internal fertilization the embryo develops and is taken care of inside the mothers body. The advantages to internal fertilization are, it protects the egg. The embryo is isolated inside the female body and there is a greater chance for a successful fertilization. Some disadvantages of internal fertilization are, there are more limited amounts of offspring being created at any specific time. There are risks of catching sexually transmitted diseases. Sometimes it is harder for the male and female species to come in contact of each other.

External Fertilization

Through the process of spawning, male and female fish and sea urchin release there sperm and egg cells that will unite outside of there bodies. When the sperm cell meets with the egg cell the fertilization process begins. External fertilization is more common for species living in the water. Some advantages of external fertilization are there are normally large numbers of offsprings produced. It is easier to find mate to create offsprings because gametes released often drift from wind and waves in the water. With external reproduction there can be more genetic variations of the offspring. Some disadvantages to external reproduction are there is no guarantee that the sperm will come in contact with the egg, leaving it unfertilized and wasted. There are environmental hazards such as predators which gives no guarantee the offspring will survive. -Angelina Johnston

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