Q. 1) How is diapause different from hibernation?
Ans: Diapause and hibernation are both ways to avoid the stress of the unfavourable environment. When animals want to avoid cold winter season, they undergo a state of suppressed metabolic activities or become dormant and this is called hibernation. They hide in their shelters, thereby avoiding the harsh winter climate. This phenomenon is commonly seen in bears, rodents, etc. Diapause is a stage of suspended development and reduced physiological activity under unfavourable environmental conditions. This is mostly seen in zooplankton species in lakes and ponds.
Q. 2) If a marine fish is placed in a fresh water aquarium, will the fish be able to survive? Why or why not?
Ans: The salt concentration in the sea is in the range of 30-35 (measured as salinity in parts per thousand) as compared to the freshwater aquarium in which salt concentration remains less than 5. The body of a marine fish is adapted to high salt concentration. If they are placed in freshwater, they cannot survive due to osmotic pressure problems. The water will enter their body through the process of osmosis (from low to high salt concentration) and the fish will not be able to bear the sudden change in the osmotic pressure. The body will swell and eventually burst.
Q. 3) Define phenotypic adaptation. Give one example.
Ans: A form of biological adaptation in organisms that occurs through behavioural changes in individuals is called phenotypic adaptation. Such changes occur so that the organisms can cope well under the environmental conditions that they face in their natural habitat.
Example: Giraffes have long necks so that they can eat leaves from tall trees.
Q. 4) Most living organisms cannot survive at temperature above 45°C. How are some microbes able to live in habitats with temperatures exceeding 100°C?
Ans: Most living organisms cannot survive at temperatures above 45°C. However, some microbes, known as thermophiles are able to live in habitats with temperatures exceeding 100°C due to the presence of enzymes which are stable to heat. These thermostable enzymes do not denature under high temperatures allowing the metabolic activities of bacteria to go on.
Q. 5) List the attributes that populations but not individuals possess.
Ans: The attributes that populations but not individuals possess are mentioned below:
- Birth Rate: It is the rate at which new individuals are added to the population due to birth and is also known as natality. The birth rate is the total number of births per 1,000 individuals of a population each year.
- Death Rate: It is also known as mortality and is the number of deaths in a given population per unit of time. The mortality rate is typically expressed in units of deaths per 1000 individuals per year.
- Sex Ratio: The ratio of males and females in a population.
- Age Distribution: Age distribution is the proportionate number of persons in successive age categories in a given population at any given time. If plotted, the structure is called age pyramid.
- Population Density: Population density is the total number of individuals of a species per unit area or volume at a given time.
Q. 6) Name important defence mechanisms in plants against herbivory.
Ans: Plants have evolved several defence mechanisms to protect themselves from herbivores.
Morphological Defence Mechanisms:
- Thorns e.g. Cactus, Acacia
- Mechanical protection like hairs, trichomes, spines, thicker leaves
Chemical Defence Mechanisms:
- Poisonous chemicals e.g. cardiac glycosides in Calotropis
- Nicotine, caffeine, quinine, opium, strychnine
Indirect defences include volatile compounds that attract natural enemies of herbivores.
Q. 7) An orchid plant is growing on the branch of a mango tree. How do you describe this interaction?
Ans: This interaction is called commensalism. The orchid benefits by getting support and sunlight while the mango tree is neither harmed nor benefitted.
Q. 8) What is the ecological principle behind biological control of pests?
Ans: Predators keep the prey population under check by consuming it.
Q. 9) Distinguish between:
(a) Hibernation and Aestivation
Hibernation: Dormant state during winter.
Aestivation: Dormant state during summer.
(b) Ectotherms and Endotherms
Ectotherms: Depend on environment for body temperature.
Endotherms: Maintain body temperature internally.
Q. 10) Write short notes on:
(a) Adaptations of desert plants and animals
Xerophytes show adaptations like CAM photosynthesis, thick cuticle, reduced leaves. Desert animals avoid heat, conserve water and show aestivation.
(b) Adaptation of plants to water scarcity
Plants show drought-escaping, drought-evading, drought-enduring and drought-resisting strategies.
(c) Behavioural adaptations in animals
Includes migration, hibernation, camouflage, group living etc.
(d) Importance of light to plants
Light is essential for photosynthesis, phototropism and flowering.
(e) Effect of temperature and water scarcity on animals
Animals adapt morphologically and physiologically to extreme temperatures and water availability.
Q. 11) List the various abiotic environmental factors.
Ans: Temperature, water, light and soil.
Q. 12) Give examples of:
(a) Endothermic animal – Cow
(b) Ectothermic animal – Crocodile
(c) Organism of benthic zone – Sea star
Q. 13) Define population and community.
Ans: A population is a group of organisms of the same species living in a defined area. A community is a group of populations living together.
Q. 14) Define and give one example:
(a) Commensalism: Cattle and egret
(b) Parasitism: Tick on dog
(c) Camouflage: Leaf insect
(d) Mutualism: Sea anemone and hermit crab
(e) Interspecific competition: Lions and hyenas
Q. 15) Describe logistic population growth curve.
Ans: Population growth shows lag phase, exponential phase and then slows down as it reaches carrying capacity (K), forming an S-shaped curve called the logistic curve.
Q. 16) Select the correct statement explaining parasitism.
Ans: (d) One organism is benefitted, other is affected.
Q. 17) List three important characteristics of a population.
Ans: Population size, population density and growth rate.