(ii) Environmental resistance. The factors such as shortage of food, disease, predation, environmental natural calamities which impose a check on population size constitute environmental resistance. Environmental resistance decreases the rate of population growth.
(iii) Carrying capacity. It is a measure of the feeding capacity of an environment or ecosystem for a population of a species under a given set of conditions. If the population reaches its carrying capacity then the no further growth of the pooulation takes place.
Organisms living in polar regions have to face the severe winter and show different types of adaptations.
(i) They have thick fur and more amount of fat for insulation from the cold.
(ii) During extreme winter they undergo hibernation during which their metabolic activities slow down and they sleep for a long period to avoid the harsh cold condition.
(iii) They have shorter ears and limbs to minimise heat loss.
What is altitude sickness and how does our body recover from this?
In a population these rates refer to per capita births.
Example. If in a pond there are 20 plants last year as through reproduction
In a population these rates refer to per capita births.
Example. If in a pond there are 20 plants last year as through reproduction 8 new plants are added. Taking the current population to 28 we calculate birth rate as F/20 = 0.4 offspring per plant.
(b) Attributes which a population shows and not individual.
1. Death ratio.
2. Sex Ratio.
Adaptation | Example | Process and mechanism |
Hibernation | Northern ground squirrels | Sleep during winter; body temperature drops, breathing and heart beat becomes slow. |
Aestivation | Ground squirrels in southwest deserts | Avoids heat by spending dry-hot period in a torpid state into burrows. |
Camouflage | Praying mantis | Mimics a dead leaf and resembles background vegetation. |