Write Dicotyledonous and Monocotyledonous Leaves.

Question: 

Write Dicotyledonous and Monocotyledonous Leaves.

Answer:

Dicotyledonous and Monocotyledonous Leaves

Dicot Leaf

Dicotyledonous leaf shows reticulate venation.

• Lamina consists of epidermis, mesophyll and vascular system.
• The epidermis is covered by cuticle and stomata; abaxial epidermis (lower surface) possesses more stomata than adaxial epidermis (upper surface). Sometimes adaxial epidermis lack stomata.
• Mesophyll, (parenchymatous cells) composed of the palisade and spongy parenchyma is present in between the adaxial epidermis and abaxial epidermis.
• The chloroplasts present in mesophyll perform photosynthesis in leaves.
• Vascular bundles are surrounded by bundle sheath cells and form the veins and midrib.

Monocot Leaf

Monocotyledonous leaves are characterized by parallel venation. The anatomy of a monocot leaf includes:

• Both adaxial epidermis and abaxial epidermis bear stomata.
• There is no differentiated palisade and spongy parenchyma of the mesophyll.
• Bulliform cells are present, which is developed from adaxial epidermal cells and the veins.
• Bulliform cells are large, void cells which are responsible for the curling of leaves for minimal loss of water.

Write Dicotyledonous and Monocotyledonous Roots.

Question:

Write Dicotyledonous and Monocotyledonous Roots.

Answer:

Dicot Root

• Dicot plants have the taproot system.
• The outermost layer is called the epidermis. The epidermal cells sometimes project out which appear as the root hairs.
• The epidermis is followed by the multi-layered cortex, loosely made of the parenchyma cells with intercellular spaces.
• The inner layer of the cortex is called endodermis, which is tightly packed by the barrel shaped-cells.
• Endodermis is followed by pericycle, which are a few layers of thick-walled parenchyma cells.
• In dicots, the central pith is not distinct.
• There are two to four xylem and phloem.
• The xylem and phloem are remarked by a layer of parenchymatous cells known as conjunctive tissue.

During secondary growth, the cambium separates the xylem and phloem. Pericycle, vascular bundles and pith fuse to form stele in dicots.

Monocot Root

Monocot roots do not show much difference in the anatomy from that of the dicot roots.

• Monocot plants possess an adventitious root system.
• As in the dicots, the epidermis forms the outermost layer, followed by cortex, pericycle, endodermis, vascular bundles (xylem and phloem) and pith (random order).
• Pith is conspicuous and large.
• The number of xylem in a monocot is six or more.
• Secondary growth is not seen in the monocot plants.

Write Dicotyledonous and Monocotyledonous Stem.

Question: 

Write Dicotyledonous and Monocotyledonous Stem.

Answer

Dicot Stem

The dicotyledonous stem is usually solid. The transverse section of a typical young dicotyledonous stem consists of the following parts:

• The epidermis is the outermost protective layer, which is covered with a thin layer of cuticle.
• Epidermis possesses trichomes and a few stomata.
• Cortex is multi-layered cells sandwiched between epidermis and pericycle.
• The outer layer, hypodermis (collenchymatous cells), the cortical layers (parenchymatous cells) and the inner layer, endodermis together make up the three subzones of the cortex.
• Next to endodermis is the pericycle, which is constituted of semi-lunar patches of sclerenchyma.
• ‘Circled’/ ‘ring’ arrangement of vascular bundles is present only in dicot stem.
• The Vascular bundle is conjoint, open and with endarch protoxylem.
• Pith is evident and is made of parenchymatous cells.

Monocot Stem

Monocot stem is usually hollow with no secondary growth. The anatomy of monocot and dicot stem are similar, however, some notable differences are as follows:

• The hypodermis of the cortex in monocots is made of sclerenchymatous cells.
• Vascular bundles are numerous, but scattered, conjoint and closed, surrounded by the ground tissue.
• Phloem parenchyma is absent.

Write major classes of Biomolecules.

Question:

Write major classes of Biomolecules.

Answer:

There are four major classes of Biomolecules –  Carbohydrates, Proteins, Nucleic acids and Lipids. Each of them is discussed below.

Carbohydrates

Carbohydrates are chemically defined as polyhydroxy aldehydes or ketones or compounds which produce them on hydrolysis. In layman’s terms, we acknowledge carbohydrates as sugars or substances that taste sweet. They are collectively called as saccharides (Greek: sakcharon = sugar). Depending on the number of constituting sugar units obtained upon hydrolysis, they are classified as monosaccharides (1 unit), oligosaccharides (2-10 units) and polysaccharides (more than 10 units). They have multiple functions’ viz. they’re the most abundant dietary source of energy; they are structurally very important for many living organisms as they form a major structural component, e.g. cellulose is an important structural fibre for plants.

Proteins

Proteins are another class of indispensable biomolecules, which make up around 50per cent of the cellular dry weight. Proteins are polymers of amino acids arranged in the form of polypeptide chains. The structure of proteins is classified as primary, secondary, tertiary and quaternary in some cases. These structures are based on the level of complexity of the folding of a polypeptide chain. Proteins play both structural and dynamic roles. Myosin is the protein that allows movement by contraction of muscles. Most enzymes are proteinaceous in nature.

Nucleic Acids

Nucleic acids refer to the genetic material found in the cell that carries all the hereditary information from parents to progeny. There are two types of nucleic acids namely, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The main function of nucleic acid is the transfer of genetic information and synthesis of proteins by processes known as translation and transcription. The monomeric unit of nucleic acids is known as nucleotide and is composed of a nitrogenous base, pentose sugar, and phosphate. The nucleotides are linked by a 3’ and 5’ phosphodiester bond. The nitrogen base attached to the pentose sugar makes the nucleotide distinct. There are 4 major nitrogenous bases found in DNA: adenine, guanine, cytosine, and thymine. In RNA, thymine is replaced by uracil. The DNA structure is described as a double-helix or double-helical structure which is formed by hydrogen bonding between the bases of two antiparallel polynucleotide chains. Overall, the DNA structure looks similar to a twisted ladder.

Lipids

Lipids are organic substances that are insoluble in water, soluble in organic solvents, are related to fatty acids and are utilized by the living cell. They include fats, waxes, sterols, fat-soluble vitamins, mono-, di- or triglycerides, phospholipids, etc. Unlike carbohydrates, proteins, and nucleic acids, lipids are not polymeric molecules. Lipids play a great role in the cellular structure and are the chief source of energy.

Write Difference between Red Blood Cells and White Blood Cells.

Question:

Write Difference between Red Blood Cells and White Blood Cells.

Answer:

Difference between Red Blood Cells and White Blood Cells:

The significant differences between red blood cells and white blood cells are as follows:

RBC – Red Blood Cells	WBC – White Blood Cells
Red blood cells are called Erythrocytes.	White Blood Cells are called Leucocytes or Leukocytes.
RBCs have a bi-concave disc shape	WBCs have an irregular shape.
Size varies from 6 – 8 µm in diameter.	Size varies from 12 – 17 µm in diameter.
The lifespan of RBC is about 120 days.	The lifespan of WBC is around 12-20 days after which they are destroyed in the lymphatic system
Red blood cells do not have a nucleus on maturity.	WBCs are characterized by the presence of a large central nucleus.
Due to the presence of haemoglobin, these cells appear red in colour.	These cells are colourless, as they do not have any pigment.
Only one type of RBC exists.	Different types of WBCs are found in the blood such as neutrophils, B lymphocytes, T lymphocytes, monocytes, basophils, eosinophils.
They help in the transport of respiratory gases to different parts of the human body	They help in producing antibodies to fight against disease-causing microbes.
RBCs are produced in the red bone marrow	These cells are produced in the red bone marrow, lymph nodes, and spleen.
The components of red blood cells are haemoglobin.	The components of white blood cells are antibodies with the presence of MHC (major histocompatibility complex) antigen cell markers.
These cells make up around 36-50% of human blood.	They make up around 1% of the human blood.
RBC count: 5 million/ mm³ of blood.	WBC count: 7000–8000/mm³ of blood.
The process of formation of RBC is known as erythropoiesis.	The process of formation of WBC is known as leukopoiesis.
These cells move between the cardiovascular systems.	These cells move between the cardiovascular and lymphatic systems.
Low count of RBCs results in Anaemia.	Low count of WBCs results in Leukopenia.

Write Features and Significance of Meiosis.

Question:

Write Features and Significance of Meiosis.

Answer:

Features of Meiosis

• It results in the formation of four daughter cells in each cycle of cell division.
• The daughter cells are identical to the mother cell in shape and size but different in chromosome number.
• The daughter cells are haploid.
• Recombination and segregation take place in meiosis.
• The process occurs in the reproductive organs and results in the formation of gametes.
• The process is divided into two types-Meiosis-I reduces the chromosome number to half and is known as reductional division. Meiosis-II is just like the mitotic division.

Significance

1. Meiosis is responsible for the formation of sex cells or gametes that are responsible for sexual reproduction.
2. It activates the genetic information for the development of sex cells and deactivates the sporophytic information.
3. It maintains the constant number of chromosomes by halving the same. This is important because the chromosome number doubles after fertilization.
4. In this process independent assortment of maternal and paternal chromosomes takes place. Thus the chromosomes and the traits controlled by them are reshuffled.
5. The genetic mutation occurs due to irregularities in cell division by meiosis. The mutations that are beneficial are carried on by natural selection.
6. Crossing over produces a new combination of traits and variations.

 

Write Major Endocrine Glands.

Question:

Write Major Endocrine Glands.

Answer:

Major Endocrine Glands

Pituitary gland

Enclosed deep within the skull, the pituitary gland is the size of a pea. It hangs on a stalk at the base of the brain. It consists of an anterior portion that produces hormones and a posterior portion that has many neural links. This gland is regarded as the master gland as it controls the functions of all the other glands (such as the adrenal, thyroid glands) in the endocrine system. The pituitary gland stimulates the adrenal gland to secrete cortisol, a steroid hormone controls a range of activities from controlling the body’s metabolism to stimulating blood pressure. The pituitary gland also secretes prolactin, which stimulates the production of milk.

Thyroid gland

The thyroid glands can be found at the front of the neck. It sits low in the throat, between the windpipe. Brownish red, it has blood vessels coursing through it. It secretes hormones that are collectively called thyroid hormones. The most prominent are T3 and T4, which influence the body’s rate of metabolism.

Parathyroid glands

The parathyroid glands consist of four small glands that are located behind the thyroids in the neck. They influence the calcium levels in the body by producing a hormone called Parathyroid Hormone. Sometimes, when the gland produces excess parathyroid hormones, it can have negative effects such as brittle bones and kidney stones.

Adrenal glands

The adrenal glands sit atop the kidneys and are no larger than a walnut. These glands produce over 150 hormones that regulate different functions in the body. The most well known is Adrenaline, which triggers the flight or fight response. In other words, this is a stress hormone that helps the organism to either face a dangerous situation or to avoid it altogether. It does this by:

• Increasing blood sugar levels
• Increasing the blood supply to the muscles, particularly to the limbs.
• Dilating the pupils
• Increasing the heart rate
• Tightening the jaw muscles.

Pancreas

The pancreas is exocrine as well as an endocrine gland that sits behind the stomach. It is roughly 6 inches long and rather flat. The pancreas has two primary roles to play:

• Producing digestive enzymes
• Producing hormones such as insulin and glucagon.

Insulin is produced by the β cells in the pancreas and it helps in regulating the blood glucose levels in the body from getting too high. As we are all aware, the lack of insulin causes type 1 and type 2 diabetes. The hormone glucagon is produced by α cells of the pancreas and it helps the body to prevent the glucose levels from dropping too low. Lack of glucagon leads to hypoglycemia. Another key difference between the two is insulin becomes active when the blood glucose levels are high, and glucagon become active only when blood glucose levels are low.

Gonads

Some glands are specific to males or females. For instance, the ovaries are specific to females and are located in the pelvic cavity. While the testes are specific to males. Ovaries produce estrogen that is important for reproduction and female sex characteristics. Testes produce testosterone that is responsible for male sex characteristics. Also, it results in increased muscle mass and body hair.

Pineal gland

The pineal gland is located between the two halves of the brain. It was also known as the “third eye” for most of history due to its location in the brain and its connection with light.

It produces a hormone known as melatonin which influences the body’s internal clock. Also known as the Circadian Rhythm, it influences the body’s sleep/wake cycle. Its effects are not really noticeable unless the individual is sleep-deprived. Factors such as jet lag, or working the night shift has a more noticeable effect on an individual because Circadian rhythm tends to coincide with the day and night cycle. That’s why individuals who work during the night find it hard to fall asleep during the day, and consequently stay awake for the next night.