page 3

Question 1

Sexual Reproduction and Meiosis (processes and products)

Answer 1

Offspring’s produced differ genetically from their parents and from each other. Diploids produce haploid gametes that fuse at fertilisation to produce a diploid zygote.
Meiosis is the process that produces gametes with a haploid number of chromosomes, in comparison to somatic cells, which have a diploid number. Four genetically different haploid gametes are produced after each cycle of meiosis. Gametes originate from diploid somatic cells in a reduction division

Question 2

Comparison of Mitosis versus Meiosis

Answer 2

Meiosis and Mitosis, both go through similar stages and need to separate sister chromatids. However, in meiosis the cell has a more complex task and must separate homologous chromosomes. Mitosis has two identical daughter cells while meiosis has four unique.

Question 3

Advantages and Disadvantages of sexual reproduction

Answer 3

Advantages: more resistance against diseases, genetic variation amongst offspring’s
Disadvantages: energy consuming, mate needed, long pregnancy, high level of parental care and produces small numbers of offspring

Question 4

Types of embryonic germ layers and the specialised tissues they form

Answer 4

Ectoderm - the outer layer of the embryo, it forms the epidermis, hair, peripheral nervous system, brain and spinal cord
Mesoderm - middle layer of the embryo, forms muscle, cartilage, kidney, gonad cells
Endoderm - innermost layer of the embryo, forms the lungs, bladder, digestive system lining, stomach, colon, liver and pancreas

Question 5

Embryonic versus Adult Stem Cells

Answer 5

Embryonic Stem Cells are the undifferentiated cells of embryos (from the zygote to blastocyst stage). ESC’s can become many types of cell and can replicate indefinitely. Used for the growth and development of the embryo.

Adult Stem Cells are present in small numbers in some adult tissues (hair follicles, bone Marrow, spinal cord, germ cells) and remain as stem cells for life but can give rise to other limited numbers of cell types. Adult Stem Cells are used in the repair and regeneration of damaged and aged tissue. They can’t replicate indefinitely.