Ecology Of Population

To understand overcrowding, we need to consider factors that increase or decrease a population within a certain area.

High natality refers to a high birth rate. When more individuals are born in an area than those leaving it, the population will naturally increase, potentially leading to overcrowding as the area becomes inhabited by more individuals than it can comfortably support. This is because more births without corresponding departures or deaths means more people vying for the same resources.

Emigration is the process of individuals moving out of a given area to live elsewhere. This movement decreases the population of an area, which would typically help prevent overcrowding rather than cause it. Hence, emigration does not lead to overcrowding.

Competition involves individuals or species competing for limited resources such as food, water, or territory. While it does not directly cause overcrowding, high population density due to overcrowding can intensify competition since more individuals fight for the same scarce resources. Thus, competition is more of a consequence rather than a direct cause of overcrowding.

High mortality means a high death rate. This reduces the number of individuals in a population, which works against overcrowding. With more individuals dying, the population decreases or stabilizes, alleviating pressures that lead to overcrowding.

In summary, among the listed factors, high natality is the most significant contributor to overcrowding as it directly increases population size when not matched by increased emigration or mortality.

(a) Four adaptive features of animals that climb rain forest trees

• Long, curved claws or nails for gripping bark and branches.
• Prehensile (grasping) tail or limbs for holding on to branches.
• Opposable digits (fingers and toes) for firm grasping.
• Adhesive pads/suckers on toes (as in tree frogs) and strong, well-developed limb muscles for climbing and leaping.

(b) Five important uses of water to organisms in the tropical rain forest

• Water is the medium (raw material) for photosynthesis in green plants.
• It is a solvent and medium for transport of dissolved food, minerals and wastes within organisms.
• It is needed for germination of seeds and for turgidity/support in plants.
• It serves as a habitat for aquatic organisms and for drinking by animals.
• It aids temperature regulation (cooling by transpiration and sweating) and biochemical reactions.

(c) Measuring temperature as an ecological factor: temperature is measured using a thermometer. Air (atmospheric) temperature is read from a mercury or alcohol thermometer placed in shade; soil temperature is taken with a soil thermometer buried at the required depth; and maximum-minimum (six's) thermometers record the highest and lowest temperatures over a period. Readings are taken in degrees Celsius.

(d)(i) Two scientists who contributed to the study of evolution: Charles Darwin and Jean-Baptiste Lamarck (Alfred Russel Wallace also acceptable).

(ii) Five evidences supporting the occurrence of evolution

• Fossil records showing gradual change of organisms over time.
• Comparative anatomy (homologous and vestigial structures).
• Comparative embryology (similar early embryonic stages).
• Geographical distribution of organisms.
• Cell biology / biochemistry (similar cell structure and molecules such as DNA and proteins).