Migrate:
- The organism moved away temporarily from the stressful habitat to a more hospitable area and return when stressful condition is over.
- Bird migrate form the colder region to warmer region.
Suspend:
- Thick walled spores are formed in microbes to overcome unfavourable stressful external environment. Spores germinate in favourable condition.
- In higher plants seeds and other vegetative reproductive structures are means to tide over the stress. They reduce their metabolic activity and going into a state of ‘dormancy’.
- Hibernation: during winter animals like bears escape in time
- Aestivation: animals like snail and fish avoid summer related problem like heat and desiccation.
- Diapauses: many zooplanktons undergo a stage of suspended development in unfavourable conditions.
ADAPTATION:
- Adaptation: is any attribute of the organism (morphological, physiological, and behavioral) that enables the organism to survive and reproduce in its habitat.
Adaptation of animal in desert:
- Kangaroo rat meets their water requirement from oxidation of fat.
- Excrete very concentrate urine to conserve water.
Adaptation of plant in desert (xerophytes)
- Thick cuticle on their leaf surfaces.
- Sunken stomata, both to reduce transpiration.
- Have special photosynthetic pathway (CAM), stomata closed during day time and remained open during night.
- Opuntia has no leaf- they are reduced to spines.
- Photosynthesis takes place in flat green stems.
Adaptation of animal in cold climate:
- Allen’s Rule: mammals from colder climates generally have shorter ears and limbs to minimize heat loss.
- Seals of polar aquatic seas have a thick layer of fat called blubber below their skin that acts as insulator and reduces loss of body heat.
Adaptation in high altitude:
- A person move to high altitude (>3,500 meter), develop altitude sickness.
- Symptoms developed are nausea, fatigue and heart palpitations.
- This is due to low atmospheric pressure of high altitudes; the body does not get enough oxygen.
How the bodies solve the problem?
- The body compensates low oxygen availability by increasing red blood cell production.
- The body compensates decreasing binding capacity of hemoglobin with oxygen by increasing rate of breathing.
Behavioral adaptation:
- Desert lizards are conformer hence they cope with the stressful environment by behavioral adaptations:
- They bask in the sun and absorb heat when their body temperature drops below the comfort zone in winter.
- Move to shade when the ambient temperature starts increasing.
- Some species burrowing into the soil to hide and escape from the above-ground heat.
POPULATION:
Population attributes:
- Population: a group of individual living in a well defined geographical area, share or compete for similar resources, potentially interbreed.
- Birth rate and death rate refers to per capita births and deaths respectively.
- Another attribute is sex ratio. The ratio between male female in a population.
- If the age distribution is plotted for a population the resulting structure is called age pyramid.
- The shape of the pyramids reflects the growth status of the population like growing, stable or declining.
- The population size is more technically called as population density.
Methods for measurement of population density:
- Counting the number
- Percent cover
- Biomass.
- Pug marks and fecal pellets for tiger census
CBSE Biology (Chapter Wise) Class XII ( By Mr. Hare Krushna Giri )
Email Id : [email protected]
