Population

1 Mark Questions

1.State Gause's competitive exclusion principle. [Ail India 2014]

Ans. Gause's competitive exclusion principle states that two competiting species for same resource cannot co-exist, if all other ecological factors are constant.

1. Write, what do phytophagous insects feed on? [Delhi 2012] Ans. Phytophagous insects feed on sap and other parts of plants.
2. What is the interaction called between Cuscuta and shoe flower bush? [Delhi 2012] Ans. The interaction between Cuscutaand shoe flower bush is called parasitism. Here, Cuscuta is the parasite which infests the shoe flower bush and derives nutrition from it
3. What is an interaction called when an orchid grows on a mango plant? [Delhi 2012]

Ans. An orchid growing on the branch of a mango tree is an epiphyte. Epiphytes are plants growing on other plants which however, do not derive nutrition from them. Hence, the relationship between a mango tree and an orchid is an example of commensalism.

1. Mention the unique feature with respect to flowering and fruiting in bamboo species.

[Delhi 2012]

Ans. Bamboo plants flower only once in their life time, generally after 50-100 years, produce large number of fruits and then die.

6.In a pond, there were 20 Hydrilla plants. Through reproduction, 10 new Hydrilla plants were added in a year. Calculate the birth rate of the population. [Delhi 2012]

Ans.

The birth rate of Hydrilla Number of individuals born Total number of individuals <math>=\frac{10}{20} = 0.5</math> per Hydrilla plant per year Birth rate is 0.5 per Hydrilla plant or 500/thousand/year. (1)

1. Pollinating species of wasps show mutualism with specific fig plants. Mention the benefits

the female wasps derive from the fig trees from such an interaction. [All India 2011] Ans. The wasp uses the ovary for oviposition. It also uses the developing seeds of the fruit to nourish its larvae.

1. Why are cattle and goats not seen browsing on Calotropis growing in the fields? [Foreign 2011]

Ans. Calotropis plant produces poisonous cardiac glycosides. Therefore, cattle or goat do not graze these plants

1. If 8 individuals in a laboratory population of 80 fruitflies died in a week, then what would

be the death rate for population for the said period? [Delhi 2010] Ans.

Death rate = <math>\frac{\text{Number of individual died}}{\text{Total number of individuals}}</math><br>= <math>\frac{8}{80}</math> = 0.1 individuals/week

Death rate will be 0.1 individuals /week.

10.In a pond, there were 200 frogs.40 more were bom in a year. Calculate the birth rate of the population. [Delhi 2010]

Ans.

The birth rate of frog population

<math>=\frac{40}{200} = 0.2 \text{ per frog/year}</math>

or 200 per thousand/year.

1. Why do predators avoid eating Monarch butterfly? How does the butterfly develop this protective feature? [Foreign 2010]

Ans. Predators avoid the monarch butterfly as it is highly distasteful to its predators (birds) because of a special chemical present in its body. It acquires this chemical during the caterpillar stage by feeding on a poisonous weed

12.Comment on the interaction between a clown fish living among the tentacles of a sea anemone.[Delhi 2010]

Ans. The interaction between a clown fish living among the tentacles of sea anemone is called commensalism.

1. Comment on the interaction between certain species of fig trees and Wasps. [Delhi 2010c]

Ans. The relation between fig trees and wasps is of mutualism.

1. Name the type of interaction seen between whale and barnacles growing on its back.

[Foreign 2009]

Ans. The type of interaction observed between whale and barnacles growing on its back is commensalism.

1. How does camouflage help an insect? [All India 2009 C]

Ans. Camouflage is a prey defence mechanism to avoid being detected easily by the predators.

16.Mention any two significant roles predation plays in nature.[All India 2008]

Ans. Significant roles played by predators are predators keep prey population under control. They help in maintaining species diversity in a community by reducing the intensity of competition

17.List two advantages that a mycorrhizal association provides tO the plant. [All India 2008 C]

Ans. Mycorrhizal association helps plants in

1. Providing resistance to root borne pathogens.
2. Absorbing nutrients.