14) Explain concepts of genetics: allele, homozygote, heterozygote, dominant, recessive, linked genes.

• Allele: An allele is the one pair of genes, one coming from the mother, the other from the father, in the chromosomes of a living things.

• Homozygote: Having identical alleles for a given trait.

• Heterozygote: Having two different alleles for a given trait.

• Dominant gene: The gene that is always expressed and prevents the expression of another gene.

• Recessive gene: The form of gene that is expressed only when paired.(aa)

• Linked gene: More than one gene on a single chromosome. Linked genes can be separated from each other by crossing over in meiosis.

15) Characteristics of birds.

The characteristics that qualify birds are:

• warm blooded (endothermic)

• vertebrates (they have a backbone and an internal skeleton)

• breathe using lungs (not gills)

• an outer covering of feathers - this feature is not shared with any other vertebrate group

• reproduce by laying eggs

Other features which are characteristics of birds, but not used to set them apart from other vertebrate groups, include:

• All birds have wings, but not all birds fly: generally, there is reduction of skeletal weight

• Birds have beaks or bills, and do not have teeth

• Birds have two legs

• Birds have a cloaca, a cavity into which the intestinal, urinary, and genital canals empty

• Birds have nucleated red blood cells, unlike mammals

• Birds have a chambered heart.

• Egg-Laying: All birds lay amniotic eggs as part of their reproductive cycle.

• Communication: Birds have highly developed communication skills, and many bird species communicate vocally through elaborate songs and calls.

• High Metabolism: Birds have a high, efficient metabolism that quickly turns food into usable energy. 

16) Blood and its components: plasma, erythrocytes, leucocytes, thrombocytes.

Blood is the life-maintaining fluid that circulates through the body’s:

• Heart, arteries, veins and capillaries.

It consists of 45% of cells and 55% of plasma. There are approximately 15 L of fluid in an adult human body.

1. PLASMA

Plasma constitutes 55% of the blood, of which 90-92% is water, 7-9% plasma proteins, and the remaining 1% is amino acids, carbohydrates, lipids, hormones, urea, uric acid, lactic acid and other trace elements.

There are more than 70 different types of plasma proteins. 3 of them are well-known and have important functions.

• Fibrinogen is involved in blood clotting.

• Albumin regulates osmotic pressure of the blood and interstitial flid.

• Globulins participate in the structure of antibodies.

Most blood proteins are produced by the liver. The glucose level of blood is approximately 80-120 mg per 100 ml. Plasma carries nutrients, blood cells, and other substances.

2. BLOOD CELLS

• The erythrocytes are the most numerous blood cells. There are 4-6 million per mm³. They are also called red blood cells. At high altitudes, greater amounts of erythrocytes. Erythrocytes don’t contain a nucleus. They contain hemoglobin, which fills almost the entire cytoplasm. Erythrocytes function in the transport of oxygen.

• Leucocytes are nucleated, spherical, white cells. They are responsible for defense of the organism. They help fight infections and aid in the immune process. It is colourless.

• Thrombocytes help in blood clotting. They have characteristic ray-like surface projections. Platelets are much smaller in size than the other blood cells. They group together to form clumps, or a plug, in the hole of a vessel to stop bleeding.

Functions of the blood:

• Nutrient transport: Nutrients, such as glucose, amino acids, vitamins, minerals and oxygen, are transported to cells by the blood.

• Hormone transport: Hormones secreted by the endocrine glands enter the blood and transported to target cells or tissues.

• Homeostasis: Blood helps maintain homeostasis by regulating pH at 7.4. It also regulates water and temperature levels.

• Immune response: Invading viruses, bacteria and other foreign substances are phagocytosed by antibodies and leucocytes in the blood.