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Charles Darwin

1. Discuss why flowering plants produce flowers and fruits. Describe how a tree moves water from the ground to every leaf. Why do plants need to ‘breathe’? Flowering plants produce flowers and fruits as this is their safeguard for the continuance of their species amidst the ever changing environmental conditions. According to Sean Carrington (2005), flowering plants was described by Charles Darwin as “that abominable mystery” (1st par. ) and as such are the dominant plants on earth today with over a quarter million species.

It is a known fact that water cannot run uphill but can climb walls trough capillary action. Water can be pulled however by suction up to a height of not more than 30 feet (Summers, 2005). But trees can move up water from the ground and distribute it to all and every leaves it has. Summers (2005) revealed that in the woody portion of trees called xylem are array of narrow tubes that are responsible for carrying up water from roots to the leaves. The author added that at the top of every xylem tubes, the water evaporates into spaces under the leaves

and exit to the atmosphere through natural openings in the leaves called stomata. The process of evaporation of water through the stomata is termed as transpiration. The latter creates a capillary action which is “the electrostatic attraction between the water and the leaf cells and the inner surface of the xylem tubes that sucks the water through the xylem vessels and distribute it to the leaves” (4th par. ). Added to this, according to the author, the electrostatic affinity of water molecules with one another provide just enough cohesive force

for the entire vertical column of water not to be cut allowing water to travel upward from the roots to the top of the tree. The author further reported that water is needed by the leaves in its photosynthetic activity which absorb carbon dioxide from the atmosphere and release oxygen as a by product (9th par. ). The taking in of carbon dioxide and exhaling of oxygen by the plants can be literally considered as breathing process of the plant and is essential for its normal physiological processes to function. 2. Discuss why sexual reproduction (two sexes) is of value to the survival of animal species

over time. Describe Darwin’s concept of sexual selection and how it differs from natural selection. Sexual reproduction result to offspring with great genetic variability as they inherit the 2 variability from parents with different genetic make-up or genotype (Chapman and Reiss, 1999, p. 51). Genetic variability provide the individual animal species with dominant protection against the pressure of the ecosystem like diseases and insects and therefore ensure survival of the species over time. The survival of species over time can also be enhanced by sexual selection.

This concept of Darwin is different from natural selection where in the fittest against the brutality of the nature survive and reproduce. Sexual selection involves the struggle of male individuals for the possession of the female sex. Under this concept, the most vigorous males are those who are best fitted for their place in nature and will leave the most progeny. Chapman and Reiss (1999) in page 97 of their book explained the sexual selection example in a tribe of lion called pride. According to the authors, there were several ready to mate lioness in a tribe and will be serviced by

male lions belonging to the pride. There were cases that other male lions from different pride will fight with the male lions and even kill them for the possession of the estrous lioness and impregnate the latter resulting to more vigorous pride population. 3. Discuss why biodiversity is important for the long term survival of life on earth. Why are humans considered to be a serious threat to biodiversity? Chapman and Reiss (1999) revealed that biodiversity is a word coined in 1985 and after 1992 Rio de Janeiro summit, it became a byword to mean biological diversity.

According to the authors, biodiversity is the number of different species of life form found in a given area (p. 269). The more richer the biodiversity of a country, the more successful the conservation of natural resources done and the more the likelihood that the country can support life and survive the ravages of nature. Humans according to the authors were the greatest destroyer of biodiversity due to cultivation of natural ecosystems, aggressive farming and industrialization (p. 269). 4. Discuss the environmental factors that tend to regulate the number of individuals in

natural populations. Why do these factors not impact the growth of human populations very much? The environmental factors that effect population level in natural setting can be grouped 3 into three. The first group is the constantly limiting factors like food supply and space. These are always limited in supply and tend to affect the population level in relatively fairly constant size Chapman and Reiss (1999). Plants always compete for space, nutrient and light and birds compete for other species in nesting territories thus limiting their population level fairly constantly (p. 40).

The second group are the so called variably limiting factors which normally are predictable like limited food supply and seasonal drought and cold. Evasive action by population like seasonal migration of birds from temperate to tropics during winter and falling of leaves by deciduous trees at onset of winter (p. 40). The third group is the unpredictable factors like weather effects, high level of predation and occurrence of deadly pests and diseases. This factor contribute to irregular population decline and sometimes loss of the whole population as in the case of volcano eruption.

Human beings are not affected very much by the three factors discussed due to the fact that they can implement interventions to neutralize, limit and even cancel the effects. 5. Discuss the role of producers, consumers and decomposers in a typical ecosystem. Why there are usually few large carnivores in an ecosystem but many small decomposers? It is an accepted fact that virtually all the energy that living organisms in an ecosystem requires come from the sun. The light energy is being used by autotrophs or plants which is being considered as the universal producers of food (Chapman and Reiss, 1999). The

producers is consumed by herbivores who are the first line of consumers exemplified by man eating vegetable and fruits and cattle eating grasses (p. 5). The herbivores are then eaten by carnivores and omnivores and eaten in return by other carnivores. When the producers and consumers die, their remains is being eaten by decomposers and turn them into soil nutrients to be consumed again by producers. By way of deduction, in a balanced ecosystem, there are only few large carnivores and omnivores so that the ecosystem can support the supply of producers which they consume. On the other hand, there are quite a

number of decomposers to clean the mess of remains of carnivores and omnivores and restore the balance of the ecosystem. 4 References Sean Carrington, C. M. (2005). Reproduction in Flowering Plants. Retrieved May 29, 2009 from http://www. cavehill. uwi. edu/FPAS/bcs/cape/capefl. html Summers, A. (2005). How Trees Get High. In Biomechanics, American Museum of Natural History. Retrieved May 29, 2009 from http://www. biomechanics. bio. uci. edu/_html/nh_biomech/trees/trees. htm Chapman, J. L. and Reiss, M. J. (1999). Ecology: principles and applications. England: Cambridge University Press

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