Disadvantages and advantages of Sexual reproduction

Abstract
Sexual reproduction is the fusion of two gametes to form a zygote which develops in to a new organism Taylor (1997). Its role is to provide genetic variation needed to adapt to ever-changing environment Kent (2000). Asexual reproduction on the other hand, is reproduction by a single organism without the production of gametes Taylor (1997). It provides a much better rate of return Kent (2000). Sexual and asexual reproduction is to ensure that genetic material are transmitted from one generation to the next, ensuring that specie survive Taylor (1997).

Introduction
Sexual and asexual reproductions are suited for different environmental circumstances Solomon (2004). The process whereby a male sex cell and a female sex cell combine to form the first cell of a new individual is called sexual reproduction Alters (2000). Although sexual reproduction involves the combination of sex cells, many organisms can’t reproduce in that way and so reproduce asexually Alters (2000). Asexual reproduction can occur in all five kingdoms of life Alters (2000). Sexual and asexual reproduction both have their advantageous and disadvantageous characteristics, with respect to survival of populations and species Alters (2000).

Reproduction is the production of a new generation of individuals of the same specie Taylor (1997). Ensuring that species survives over a long period of time, depends on the transmission of genetic materials from one generation to the next Taylor (1997). In asexual reproduction, DNA simply replicates generation after generation Davis (1998). Sexual reproduction requires fertilization the fusion of two gametes to form a zygote Davis (1998). The generation of a new individual by asexual reproduction is formed without the
union of gametes Alters (2000). It is a cloning process- a method of exact replication of parental organisms Alters (2000).

Asexual reproduction requires one parent, whereas sexual reproduction usually involves two parents Fogiel (1978). The advantage of asexual organisms producing by one self is that it requires no mating to produce off springs, saving resources that would otherwise be put into courtship for example, Cavendish (2010). This advantage is probably the reason why asexual reproduction is common among sessile animals (those that cannot move about) and those that live in dispersal populations, where the chance of finding a mate is small Cavendish (2010). In sexual reproduction two parents is a disadvantage because time and energy are needed to find a mate Taylor (1997). The picture above shows star fish being reproduced asexually by fragmentation.

Picture 2

   Secondly, asexual reproduction produces genetically identical off springs Taylor (1997). The numerous off springs are genetically identical to the original parent ensures that favorable combinations of genes are perpetuated exactly Minkoff (2000). Sexual reproduction produces some individual with genotypes that are well adapted to the environment, but it also produces some individuals that are less well adapted Solomon (2004). If the organism is well adapted to its environment, the fact that it is genetically identical may be an advantage, as successful combination of genes are preserved Taylor (1997). In addition, asexual reproduction has a greater chance for its off springs to disperse and spread Taylor (1997). More generations of off springs can be produced in a small amount of time Minkoff (2000). Those organisms reproducing asexually can generally do so faster and with low energy cost Minkoff (2000).To prove this fact, bacteria can divide as often as once every 20 minutes, allowing members to build up very rapidly Taylor (1997). The picture above shows binary fission in bacteria. In comparison to sexual reproduction, they cannot produce at a very fast rate.  Example, human beings takes nine months to produce a young.

Sexual reproduction is advantageous.  It produces genetic variability (variation) among organisms of the same specie Alters (2000). When environmental conditions change, population with genetic variability can adapt and change to suit the environment overtime Alters (2000). In comparison to asexual reproduction, once the environment is unstable, the chance of an entire generation of specie to die is very high Taylor (1997). This is because asexual reproduction produce clone, as a result, if one organism is affected by the environment then all will be affected (unless in the case that one is mutated).

Sexual reproduction brings about and evolutionary advantage. By mixing genetic material from both parents, variation is encouraged Cavendish (2010).

Combinations of genes cope with change Cavendish (2010). Sexual reproduction goes through meiosis. Meiosis is an essential feature of life cycles in which sexual reproduction occurs because it provides a mechanism for reducing the amount of genetic material by half Taylor (1997). During meiosis, random segregation of chromosomes and the exchange of genetic material between homologous chromosomes results in new combinations of genes being brought together in gamete and this reshuffling increases genetic variation Taylor (1997). Refer to the picture 3.

Table showing: the comparison between asexual and sexual reproduction.

Asexual reproduction	Sexual reproduction
One parent only	Two parents
No gametes are produced	Gametes are produced. These are haploid and nuclei of two gamete fuse to form diploid zygote.
Depends on mitosis	Depends on meiosis being present at some stage in life cycle to prevent chromosome doubling in every generation
Off spring is identical to parent	Off springs are not identical to parents.
Commonly occur in more plants, simple animals and microorganisms	Occurs  in almost all plants and animal specie
Often result in rapid production of large numbers of off spring	Less rapid increase in numbers

The greatest advantage of sexual reproduction is the genetic variation that is favored whenever future conditions are uncertain Minkoff (2000). The alternation and fertilization and meiosis is common to all eukaryotic organisms and constituents the sexual life cycle Davis (1998).

Reference

·       The Gist of Genetics: Guide to learning and review. Rowland Davis et al. 1998.

·       Biology: understanding life, Sandra alters, 2000.

·       Advanced biology by Michael Kent (2000) .

·       Biology 7th edition, Eldra Pearl Solomon et al., 2004.

·       The biology problem solver: Max Fogiel research and education association, 1978.

·       Anatomy and physiology: Marshall Cavendish Corporation 2010 .

·       Biology Today: an issue approach: Eli C. Minkoff and Pamela J. Baker. 2000 .

·       Biological Science 2 : Systems maintenance and change D.J Taylor et al. 1997.

Picture1: http://www.google.com/imgres?q=asexual+animals&um=1&hl=en&sa=N&biw=1440&bih=799&tbm=isch&tbnid=K0mspbwOH5cldM:&imgrefurl=http://johnfriedmann.com/biogloss/fragmentation.htm&docid=k-4CqYmHhK-dbM&imgurl=http://johnfriedmann.com/biogloss/fragmentation.jpg&w=908&h=600&ei=y8FKT53XENOltwfr1unuAg&zoom=1&iact=hc&vpx=183&vpy=158&dur=6908&hovh=182&hovw=276&tx=141&ty=105&sig=109633011387640490567&page=1&tbnh=139&tbnw=201&start=0&ndsp=26&ved=1t:429,r:0,s:0

Picture2: http://www.google.com/imgres?q=bacterial+division&hl=en&sa=X&biw=1440&bih=799&tbm=isch&prmd=imvns&tbnid=wfPdQvZWUK-7SM:&imgrefurl=http://www.brighthub.com/education/homework-tips/articles/54480.aspx&docid=01REYAFhkSsGfM&imgurl=http://images.brighthub.com/c8/d/c8d02b1866e0a8632e85f27896fae400bf76906a_large.jpg&w=600&h=600&ei=WxhMT4zUFMLkiALPzqHDDw&zoom=1&iact=hc&vpx=709&vpy=173&dur=8801&hovh=225&hovw=225&tx=94&ty=141&sig=109633011387640490567&page=1&tbnh=140&tbnw=141&start=0&ndsp=28&ved=1t:429,r:3,s:0

Picture 3: http://www.google.com/imgres?q=sexual+reproduction&um=1&hl=en&sa=N&biw=1440&bih=799&tbm=isch&tbnid=eoDGjl81SQmrMM:&imgrefurl=http://www.ewart.org.uk/biology/index.php%3Fl%3D6&docid=fjhew4z3H1eyWM&imgurl=http://www.ewart.org.uk/biology/pics/sexual.gif&w=294&h=217&ei=OP1QT4zPEdO50QHHpY39DQ&zoom=1&iact=rc&dur=421&sig=109633011387640490567&page=1&tbnh=125&tbnw=167&start=0&ndsp=30&ved=1t:429,r:17,s:0&tx=127&ty=65

Disease. What is?

Disease

Disease can be :

1. Infectious
2. Deficiency
3. Genetic
4. Mental

1. Infectious disease- are caused by pathogenic microorganisms and has the ability to spread quickly, directly, or indirectly. Infectious disease is an invasion of a host organisms by foreign organisms, often called microbes (small and microscopic). Microbes ( example viruses, bacteria). An organism that microbe infects is called the host. Infectious disease is transmitted by a vector (i.e. agent by means of mode transfer).

2. Deficiency disease is caused by lack of a certain nutrient in a person's body. In this case a person'd diet is short of an essential nutrient. Xerophthalmia (night blindness) is a deficiency disease caused by a deficiency of vitamin A (retinal) in the diet.

3. Genetic disease is a disorder that is inherited genetically. A genetic disease is as a result of a mutation in an individual's DNA, as a result of a change in letter in a person's DNA sequence. Genetic disease can be inherited because of a mutation of gene cells in the body. This can happen when cells pass gene information from parent to offspring or by mutation of DNA sequence in a single gene. For example, sickle cell anemia is a mutated form of hemoglobin that distort the shape of the red blood cell, so it appears sickle (crescent) in shape.

4. Mental disease is a disease of the mind generally  associated with distress or disability. It is a medical condition that disrupts the way a person thinks, feel and behave. An example is depression, which is a condition of mental disturbance. The person may have difficulty in maintaining concentration or interests to life causing a feeling of sadness.

Health and Disease- What is health?

What is health?

According to the WHO, "health is a state of complete physical,mental and social well-being not merely the absence of disease or infirmity". Mental health is defined as a state of well-being in which every individual realizes his or her own potential, cope with normal stress of life and still can work productivity.

Social well-being suggests a person's relationship to others. The ability to communicate, interact and socialize with other people. It is a end state in which basic human needs are met and people co-exist peacefully in communities. This state is characterized by equal access to and of basic needs and community life society. Basically, it is having a satisfactory relationship with other people and their good attitude in life as general.

Physical well-being has to do with our bodies. It is a state free from physical signs of disease or injuries as broken limbs and keeping fit. It relates to the ability to understand what can make our bodies most efficient. A degree of physical well-being is achieved through physical strength, flexibility, endurance, nutrition and taking safety procedures as medical health care.

Mental well-being describes a level of psychological well-being, or a absence of mental disorder, its functions in thinking, learning, emotional growth resilience and self esteem. Positive mental health is a state of well-being in which we realize our abilities and can cope with life's normal stress. Basically, it is having a healthy mind free from depression and worry.

Picture Reference: http://ianluntecology.com/2014/04/06/urban-biodiversity-human-well-beingrban-well-being/

The comparisons and contrast of glycolipids and phospholipids, And its significant role in the cell

Abstract
Phospholipids and Glycolipids are made of fats. They are amphipathic compounds which are important in forming cell membrane Taylor (1997). The Phospholipids provides the basic structure of cell membrane, whereas glycolipids act as cell-cell recognition and receptor sites for chemical signals Taylor (1997). The roles of these molecules are to ensure the structure and stability of membranes Taylor (1997).

Introduction
In the early twentieth century scientists have come to believe that cells are surrounded by thin oil-like layer Loeb (1904). Hugo Fricke also determined that the Lipid Bilayer of the cell membrane was 3.3 nm thick Fricke (1925). However, later analysis shows that this assumption was incorrect, to mean that the cell membrane is a single molecular layer Dooren LJ, (1986). Gorter and Grendel drew correct conclusions that cell membrane is a lipid bi-layer Philip (1993). This theory was confirmed through the use of electron microscope in the late 1950’s.
Fats are formed by condensation reaction between fatty acid and alcohol Taylor (1997). A basic similarity of Phospholipids and Glycolypids is that they both lie in the cell membranes Taylor (1997). They are amphipathic compounds, where the phosphate group is pointing toward intra and extracellular water environment Lodish (2000). The hydrophobic fatty acid tails with the molecules interacts with water, and the other end does not Lodish (2000); as seen below.

      This is an important characteristic in the formation of membranes. Although they are amphipathic, what makes them different is the group attached to them and how their structure is suited to their function in the cell membranes.

Phospholipids make up membranes. Glycolipids are normally found on the outer surface of the cell membrane Buehler (2011). The following diagram shows the structure of a membrane.

 Glycolipids are also abundant in the plasma membrane of eukaryotic cells and are also found in exoplasmic leaflet of membranes H. Lodish (2000).

They are both derivations of fats and elite certain immune reaction. They consist of two long non-polar hydrocarbon tails linked to a hydrophilic head group Lodish (2000).

Fats and oil are made up from fatty acid and glycerol Taylor (1997). Glycerol contains three hydroxyl groups (-OH) Taylor (1997). When glycerol condenses it forms three hydrocarbon fatty acid tails Taylor (1997). The compound formed is called a triglyceride Taylor (1997).  The formation of a phospholipid is formed in a similar way. Phospholipid has a general formula R.COOH, where R represents a medium or long chain of carbon atoms Lodish (2000). In this case, R is a phosphate group Lodish (2000). One of the hydroxyl groups is replaced by a phosphate group, where the other two forms fatty acid tails Taylor (1997).

All phospholipids contains one or more acyl chains derived form fatty acids, which consists of  hydrocarbon chain attached to  a carboxylic group (–COOH)  Lodish (2000). So as a result phospholipids are considered amphipathic Taylor (1997). The phosphate head carries an electrical charge which makes it polar, (hydrophilic) whereas the fatty acid tails are non-polar and are therefore hydrophobic Taylor (1997).

     If phospholipid was spread out on the surface of water, the polar hydrophilic head will project towards the inside and outside of the cell to the aqueous environment; whereas the non-polar end (the fatty acid tails) will project into the air, to form a layer only one cell thick Taylor (1997).

     Let’s say more of this phospholipid was added on the surface of water, or shaken, what would be the arrangement then? Particles known as micelles are formed Taylor (1997). The hydrophobic part of the phospholipid minimizes contact with water by aligning themselves tightly together in the centre of the bi-layer, forming a hydrophobic core Lodish (2000). All phospholipids can pack together into the characteristic bi-layer structure Lodish (2000)

     The close packing of these hydrocarbons is stabilized by Van der Waals interactions Lodish (2000). The hydrophilic part of the phospholipid faces the aqueous environment. Ionic and hydrogen bonds will stable the interactions of the polar head group in the water Lodish (2000).This arrangement forms what we called a phospholipid bi-layer, in which two layers of phospholipidmolecules occur, Taylor (1997). This layer is the formation of cell membranes. Refer to the following picture.

       Glycolipids are formed by the association of lipids with carbohydrates Taylor (1997). They contain a hydrophobic ceramide anchor and a hydrophilic head group made up of saccharides Beuhler (2011).

A major difference between glycolipids and phospholipids lies in the extensive hydrogen bonding capacity of the glycolipids, their phase behavior is dominated by this hydrogen bonding capacity Gabius (2002). In the cell membranes, Glycolypids help to determine the blood type of an individual Del Mar (1972). In the body they play an important role in embryonic development in which the blood type of babies in mother’s womb is shared with the mother’s blood type.

     Glycolipids contain glycoprotein which is protein bonded to sugar molecule Dr. James (1998). Glycolipids work along with this protein bonded-sugar molecules to identify foreign cells Lodish (2000). The receptor site (of the glycolipid) binds to a molecule and recognizes that it is an invader Taylor (1997). They act like cell markers (as in antigen) Taylor (1997). Glycoprotein acts as location in the cell Taylor (1997). They tell your white blood cells that foreign organisms are present in the cell and needs to be destroyed Taylor (1997).

     Receptors present at the surface of the red blood cells classify our blood type (they mark our blood cells). This is why if a patient was suppose to give blood, the recipients immune system will detect and treat the donated blood from the donor as foreign. Foreign antigens are attack by the recipients’ immune system and are destroyed Del Mar (1972).

     Parts of these molecules coat the outer surface of the cell forming chemical configurations that make the surface of the cell unique, different from one type of cell to another, different from one specie to another, and even different from one individual organism to another Del Mar (1972).

     Several glycolipids and phospholipids derived from bacteria, protozoa and other plant species in recent studies found out to be as antigens for NKT cells Tsuji (2006). By a number of studies, Natural Killer T cells are known to play a protective role against cancers and other infectious diseases Tsuji (2006).

     Glycolipids differ from phospolipids because it contains no phosphate group. Glycolipids stand out as a class of its own because of the fact that the fat is connected to a sugar molecule. Dr. James (1998). Therefore, glycolipids are simply fats that are bonded to sugars. Dr. James (1998). 

Reference

·         D.J Taylor et al, (1997) Biological science 1: organisms, energy and environment, United Kingdom, Cambridge

·         Lukas K. Beuhler, (2011) What is Life? Introduction to Metabolic Biochemistry

·         Harvey Lodish, Arnold Berk, et al,(2000) Molecular Cell Biology, New York, Media Connected

·          Del Mar (1972), Biology Today, California, CRM Books.

·         Dr. Ken James (1998), Nutriology-Nutrition for Therapy and Rehabilitation, New Orleans, Paper-mill Press.

·         Tsuji M (2006) et al, Cell and Molecular Life Sciences, USA.

·         H.Gabius and S.Gabius (2002) Glycosciences: Status and Perspectives, Germany, Wiley-VCH.

·         Joeb J (December 1904) The Recent Development of Biology.

·         Fricke H (1925) The Electrical Capacity of Suspensions with Special Reference to blood: Journal of General Physiology.

·         Dooren LJ, Wiedemann LR (1986), On Bimolecular Layers of Lipids on the Chromocytes of the Blood: Journal of European Journal of Pediatrics.

·         Yeagle Philip (1993) The Membranes of Cells (2^nd ed.), Boston, Academic Press.

Biology: Can a woman get pregnant on her period?

Biology: Can a woman get pregnant on her period?: Can a woman get pregnant on her period? The answer you are seeking for. Yes she can. In fact, a woman can get pregnant at any point dur...

Can a woman get pregnant on her period?

Can a woman get pregnant on her period?

The answer you are seeking for. Yes she can. In fact, a woman can get pregnant at any point during her cycle. Whether if she is on her first day, last day or during her bleeding state. She can get pregnant. Evenly, it is correct to say that the safest way to not get pregnant is to abstain from sex. Now let’s be real. Birth control methods are not effective. In fact, it’s sometimes not the safest.

Hence forth, the only way to not get pregnant is to not have sex. Period. In fact, each time the male sex organ (penis) is inserted in to the vagina, your chances of getting pregnant, regardless of whether you are on birth control, using the rhythm method, or a condom ( or any other methods or any sort), regardless, you can get pregnant.

When a man is sexually aroused, the penis secrets a clear viscous liquid called "pre-cum".

This may also be known as pre-ejaculatory fluid or pre-seminal fluid.

What many persons don’t know is that this fluid contains sperm, (a small amount) which can be just enough to get you pregnant. So withdrawal, is not a good method of birth control.

Another factor to consider whether a woman can get pregnant is ovulation period. Ovulation is when a fertile egg is released from one of the ovaries into the fallopian tube. Ovulation period differs from woman to woman, because each one of us is different.

Menstrual cycle varies from woman to woman. The average cycle for a woman last

an average of 28 days. Now, to understand the chance of pregnancy, you have to understand your cycle. If you don’t understand your cycle you don’t understand yourself. However, it can be just as easy to lose track of your period. Why? There are many factors to consider every month.

1. Diet

2. Lifestyle

3. Exercise

4. Stress/ depression

5. Sickness etc.

These vary from person to person, every month. As a result, it may be difficult to pin point the exact

date of ovulation, even if you have a regular period. Rhythm method, not a safe method either.

What is squalene?

Did you know that " squalene", an oily substance present in human sebum is also the same substance that is present in shark liver oil. The sebum in human is what is secreted by our skin's sebaceous glands. Squalene is an organic substance and is used to make medicine.