Photosynthesis is a process used by plants and other organisms to convert light energyinto chemical energy that can later be released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", and σύνθεσις, synthesis, "putting together".[1][2][3] In most cases, oxygen is also released as a waste product. Most plants, most algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth.[4]
Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centresthat contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting of water is used in the creation of two further compounds that serve as short-term stores of energy, enabling its transfer to drive other reactions: these compounds are reduced nicotinamide adenine dinucleotide phosphate(NADPH) and adenosine triphosphate (ATP), the "energy currency" of cells.
In plants, algae and cyanobacteria, long-term energy storage in the form of sugars is produced by a subsequent sequence of light-independent reactions called the Calvin cycle; some bacteria use different mechanisms, such as the reverse Krebs cycle, to achieve the same end. In the Calvin cycle, atmospheric carbon dioxide is incorporatedinto already existing organic carbon compounds, such as ribulose bisphosphate(RuBP).[5] Using the ATP and NADPH produced by the light-dependent reactions, the resulting compounds are then reducedand removed to form further carbohydrates, such as glucose.
The word "prokaryote" is derived from Greek words that mean "before nucleus." Prokaryotic cells contain fewer organelles or functional components than do eukaryotic cells. Their four main structures are the plasma membrane, cytoplasm, ribosomes and genetic material (DNA and RNA).
The definition of a species is termed as a group of interbreeding individuals cannot be easily applied to organisms that they reproduce only or mainly by asexual methods.
Species is termed as the basic unit of classification and taxonomic rank and also unit of biodiversity. It is the largest group of organisms whereby two individuals produce fertile offspring.
They are typically by sexual reproduction. Boundary which is between closely related species they becomes unclear.
LHON (Leber Hereditary Optic Neuropathy):Is a disease that is characterized by loss of vision in young adults.
Sickle cell anemia: Is a disease characterized by production of abnormally shaped red blood cells, that is, not round in shape as normal but are 'sickle' shaped or elongated/crescent shaped.
Both diseases are heritable But LHON is caused by mutations existing in the mitochondrion thus only inherited maternally.
Sickle cell anemia is caused by mutations in the HBB gene which produces the beta subunit of hemoglobin. It is inherited from recessive genes of both parents.
There exists the same question with the following choices.
1.Meiosis produces eggs and sperm that are alike. <span>2.Meiosis provides for chromosomal variation in the gametes produced by an organism. </span> <span>3.Equal numbers of eggs and sperm are produced by meiosis. </span> <span>4.The gametes produced by meiosis ensure the continuation of any particular species by asexual reproduction. </span> The correct answer is <span>2. Meiosis provides for chromosomal variation in the gametes produced by an organism. It happened during cross-over and segregation and law of independent assortment.</span>
