ECOLOGY AND POPULATION ECOLOGY1. (a) Explain the following terms as used in ecology; biosphere , habitat, niche.

Biosphereis the global ecologicalsystem integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, hydrosphere, and atmosphere. Biosphere is the part of the earth where living things exist. The part of the earth (or planet) that is capable of supporting life. The livingthings and theirenvironment. All of theecosystemsof the earth.

Habitatis anecologicalor environmental area that is inhabited by a particular species of animal, plant, or other type of organism. It is the natural environment in which an organism lives, or the physical environment that surrounds a species population.

Niche is the place or function of a given organism within its ecosystem. Note: Different organisms may compete for the same niche. For example, in a forest there may be anichefor an organism that can fly and eat nectar from blossoms.

(b) (i) Distinguish between the underlined termsBiotic factors are the factors of an ecosystem that are alive. For example: trees, grass, bears, etc.

Abiotic factors are the factors of an ecosystem that are not living. For example: the pH of the soil, rain, rocks, etc.

(ii) Name an ecosystem that you think of, and give an example of an abiotic factor that influences the distribution of a a biotic organism in the ecosystem

Habitats of animals and plants vary widely from aquatic environments to the dry deserts. Water is essential for life and all the biotic components of the ecosystem are directly dependent on water for survival.

(iii) Whats term is used by ecologist to describe the organisms that form the base of the pyramid

Producers

2. (a) Which plant is best adapted to the dim light?X . Population is high.

(b) What is relationship X and YCan survive in dim light conditions

3. Why are so few top carnivores or tertiary consumer in ecosystem?

In a healthy ecosystem predators and prey reach a balance so that there are always enough prey animals to continue reproducing. This ensures a permanent supply of food for the predators. If the predators over hunt the prey animal, the population of prey will decline causing the predators to starve.The ecosystem will not also be balanced if there are more predators than preys.

4. The difference between density-dependent and independent factor.Density dependent factors are factors that depend of the population (density). Such as food, water, and spaceDensity Independent factors are factors that the population (density) depends on. Such as weather, natural disasters and random occurances.

5. Why do some species have many offspring at different times over the course of their live?Though many people may choose only to have one child, humans are biologically capable of having offspring many times over the course of their lives. Iteroparous vertebrates include all birds, most reptiles, virtually all mammals, and most fish. Among invertebrates, most mollusca and many insects (for example, mosquitoes and cockroaches) are iteroparous.

6. What is biogeochemical?

The movement (or cycling) of matter through a system. Nitrogen is present in the environment in a wide variety of chemical forms including organic nitrogen,ammonium(NH4+),nitrite(NO2-),nitrate(NO3-),nitrous oxide(N2O),nitric oxide(NO) or inorganic nitrogen gas (N2). Organic nitrogen may be in the form of a living organism,humusor in the intermediate products of organic matter decomposition. The processes of the nitrogen cycle transform nitrogen from one form to another. Many of those processes are carried out bymicrobes, either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth. The diagram above shows how these processes fit together to form the nitrogen cycle.

REPRODUCTION AND DEVELOPMENT

1. Describe the process of double fertilization in plants.

A single pollen grain has 2 sperm. Double fertilization occurs when 1 of these sperm combines with the egg, and the other sperm combines with a cell (this is called endosperm) That is in order for the seed to keep being produced.Seed has to be germinated, and without the extra sperm (double fertilization) the plant couldn't germinate and would go extinct.

2. Explain the role of hormone in regulation of menstrual cycle

Gonadotropin-releasing hormone (GnRH)is produced by a part of the brain called thehypothalamus. When it circulates in the blood, it causes the release of two important hormones from thepituitaryglandin another specialised part of the brain.

Follicle-stimulating hormone (FSH)is produced by the pituitary gland during the first half of the menstrual cycle. It stimulates development of the maturing ovarian follicle and controls ovum production in the female, and sperm production in the male.

Leutenizing hormone(LH) is also produced by the pituitary gland in the brain. It stimulates the ovaries to produce oestrogen and progesterone. It triggersovulation(the release of a mature ovum from the ovary), and it promotes the development of the corpus luteum.

3. Function of(a) Oestrogenis a female reproductive hormone, produced primarily by the ovaries in the non-pregnant woman. It promotes the maturation and release of an ovum in every menstrual cycle. It is also produced by the placenta during pregnancy.

(b) Progesteroneis produced by the corpus luteum in the ovary; its function is to prepare theendometrium(lining of the uterus) for the reception and development of the fertilised ovum. It also suppresses the production of oestrogen after ovulation has occurred.

4. Outline the role of positive feedback and hormone involvement in process of birth.Three of the main hormones involved with reproduction: oxytocin, endorphin, and adrenaline. These hormones play a major role in regulating the process of labor and birth, and learning about them can help you understand what will happen during labor and birth. Childbearing women and their caregivers can take actions to support or disrupt their effects, so, understanding how they work and how they are affected is important for making informed decisions.

5. The human gestation period

First trimester, the embryo really starts to take shape. The facial structures begin to form and become recognizable. Theneural tube, which will form thebrainand spinal cord, develops. Little buds emerge and grow into arms and legs.

Second trimester a fine hair calledlanugocovers its body. The kidneys and urinary tract start to produce urine and release it into theamniotic fluid. The liver begins secreting bile, and the spleen begins to aid in the production of redbloodcells.

Third fetus will finish its development and prepare for the difficultbirth process. It is now about 15 inches long and weighs between two and three pounds. Itseyesare a definite color

GROWTH

1. Intermittent is occurring at separatedintervals, havingperiodsof cessation ofactivity.

Allometric growth is phenomenon whereby parts of the same organism grow at different rates. contrast with isometricgrowth.

Isometricgrowth that occurs at the same rate for all parts of an organism so that its shape is consistent throughout development. Contrast with allometric growth.

2. (a) allometric growth curve(b) P- lymphoid tissue. Q- head. R- reproductive system.(c) As time from birth increase, size of attained of growth increase.

3. A- lag phase, growth slow because cell division occur at slow pace. Organism try to adapt new environment.B- exponential, growth rate exponential . This because the growth of organism is not hindered by any obstacles.C- Equilibrium. Organism has achieved maturity. The rate cell division is equal to the rate of cell mortality.D- negative growth, ageing process. Reduced resources of food and space