<span>The reason the two bears showed similarities is because the species have adaptations that allow them to live in the same type of biome. Biomes are large ecological areas on the earth surface which are made up of different plants, animals and other abiotic and biotic factors. Animals of the same species usually have adaptations that enable them to live in the same type of environment.</span>
B) They permit exchange between the external atmosphere and the circulatory system.
1. The passing of traits from parents to the offsprings (children) is the basis of heredity. Traits are notable features or qualities in a person, such that each individual has a different combination of traits that makes us unique from others. They are inherited from our parents and passed from generation to generation. That is to our children, then our children to their children and so on.
2. Our genes encode the instructions that define our traits. Traits are majorly defined by the instructions encoded in the genes. However, environment may influences the traits and may play an important role in shaping the traits we posses. Often times these traits may be changed by the environmental factors.
3. Each of us has thousands of genes, which are made of DNA molecules and reside in our chromosomes. Genes are functional or fundamental units of heredity. They are made up of DNA molecules, and act as instructions to make proteins, through a process of transcription and translation. Transcription involves formation of a messenger RNA which then undergoes translation in the cytoplasm to make proteins.The protein formed determine the traits of an individual.
4. In addition to our genes, the Environment we live in also helps define our traits. The expression of genes in organisms may be influenced by environmental factors, these includes the external factors where the organism lives or develops, and also the internal factors such as its hormones and metabolism.
5. Human have two complete sets of 23 chromosomes. A human being has a total of 46 chromosomes (23×2 = 46). This is referred to as a diploid number (2n). Each set is considered to be a one homologous chromosome set. This is the case of of the somatic cells or the body cells which represents a diploid number of chromosomes.
6. When parents conceive a child, each parent contributes one set of chromosomes.This enhances the passing of traits or genes to the child. The egg cell or the ovum from the mother and the sperm cell from the father contain the haploid number (n) or one set of chromosome. During conception the two combines/fuse to form a zygote which is now diploid (2n).
7. Every child receives half of its chromosomes from the mother and another half from the father. During meiosis in the gametes for both mother and father a haploid cell is formed with one set of chromosomes (haploid, n). Therefore, each child contains half number of chromosomes from the mother and the other half from the father making up the diploid number (2n).
8. This transfer takes place at conception, when the father's sperm joins the mother's egg. During conception, fertilization takes place and the sperm cell fuses with the mother cell (ovum) forming a single cell called Zygote. The zygote has the two sets of chromosomes (23 +23 = 46). The cells then divide by mitosis leading to the development of a child.
9. While most cells in our bodies have two sets of chromosomes, or a total of 46 chromosomes, egg and sperm each have 23 chromosomes. The body cells (somatic cells) contain two sets of chromosomes (diploid number, 2n) from mitosis, while the gametes have a single set of chromosomes (haploid, n), from meiosis.
