Organism and population CH – 11
1. Ecology is a subject which studies the interactions among organisms and between the organism and its
physical (abiotic) environment.
2. Ecology is basically concerned with four levels of biological organisation – organisms, populations,
communities and biomes.
3. POPULATION: Group of organisms which live in a well-defined geographical area, share or compete for
similar resources, potentially interbreed and thus constitute a population
4. Asexual reproduction is also generally considered a population for the purpose of ecological studies
5. Population ecology: population genetics and evolution
6. If in a pond there were 20 lotus plants last year and through reproduction 8 new plants are added, taking
the current population to 28, we calculate the birth rate as 8/20 = 0.4 offspring per lotus per year\
7. Another attribute characteristic of a population is sex ratio. An individual is either a male or a female but
a population has a sex ratio (e.g., 60 per cent of the population are females and 40 per cent males).
8. For human population, the age pyramids generally show age distribution of males and females in a
diagram. The shape of the pyramids reflects the growth status of the population -
(a) whether it is growing, (b) stable or (c) declining.
9. Population size, technically called population density (designated as N) (Parthenium hysterophorus)
10. Population Growth:
1. Ecology is a subject which studies the interactions among organisms and between the organism and its
physical (abiotic) environment.
2. Ecology is basically concerned with four levels of biological organisation – organisms, populations,
communities and biomes.
3. POPULATION: Group of organisms which live in a well-defined geographical area, share or compete for
similar resources, potentially interbreed and thus constitute a population
4. Asexual reproduction is also generally considered a population for the purpose of ecological studies
5. Population ecology: population genetics and evolution
6. If in a pond there were 20 lotus plants last year and through reproduction 8 new plants are added, taking
the current population to 28, we calculate the birth rate as 8/20 = 0.4 offspring per lotus per year\
7. Another attribute characteristic of a population is sex ratio. An individual is either a male or a female but
a population has a sex ratio (e.g., 60 per cent of the population are females and 40 per cent males).
8. For human population, the age pyramids generally show age distribution of males and females in a
diagram. The shape of the pyramids reflects the growth status of the population -
(a) whether it is growing, (b) stable or (c) declining.
9. Population size, technically called population density (designated as N) (Parthenium hysterophorus)
10. Population Growth:
