Ecology By Dr Mamdouh El-Sawi From John E. Petersen

First lecture

Ecology Greek Oikos = the home or household ology = study of The study of relationships among organisms and between organisms and their environment -Greek Oikos = the home or household -ology = study of -Greek Oikos = the home or household -ology = study of -Greek Oikos = the home or household -ology = study of

levels of ecological organizations: Organisms- a unique individual. Populations- group of potentially interbreeding individuals (i.e., species). Communities - all populations within an ecosystem (i.e., multiple species). ecosystems - community + physical environment. Biomes. biosphere - ecosystems of the Earth.

Hierarchy of disciplines (‘levels of organization’) – Biospherics – Environmental science – Systems ecology – Ecosystems ecology – Community ecology – Population biology –Organism biology –Histology –Cellular biology –Molecular biology –Molecular genetics –Chemistry –Subatomic physics A scaling hierarchy of natural science Increasing scales of time and space Causality from the Reductionist perspective Hierarchy of matter –Universe –Galaxies –Solar system –Planets –Earth –Biosphere –Biomes –Ecosystems –Communities –Populations –Organisms –Organ systems –Tissues –Cells –Organelles –Molecules –Atoms –Subatomic particles 5

Population Population is a group of individuals belongs to a species. Inhabiting a give location. They are alike. They are capable of breeding with one another. Examples are: sunfish in a lake, people in a city.

Population growth: a) Exponential growth. b) Limited growth.

1- a bacterium can divide by binary fission to produce two bacteria in 20min. 2-after another 20 min we’d have 4. 3-after another 20 min we’d have 8 and so on. 4- after 24 we’d have 4 x bacteria In this type of growth the size of population increases exponentially; look at fig (1).

Fig (1)

In reality this could never happen. Because Nutrients would get used up. Space would become scarce. Waste products would accumulate. Some members of the population would die. and the growth curve would flatten out as the population stabilized. Here, the maximum population size is limited.