The critical difference is that,

In short-day (i.e., winter flowering) plant species, P_FR inhibits flowering.

In long-day (i.e., summer-flowering) plant species, P_FR induces flowering.

TLS Online TPP Program

#Id: 5511

#Unit 10. Ecological Principles

Populations of some species are prone to extinction for two reasons

1. The landscapes they live in are patchy (making dispersal between populations difficult).

2. Environmental conditions often change in a rapid and unpredictable manner.

TLS Online TPP Program

#Id: 5513

#Unit 10. Ecological Principles

The size of a population is determined by a balance between births, immigration, deaths and emigration.

TLS Online TPP Program

#Id: 5515

#Unit 10. Ecological Principles

Natality means production of new individuals (offspring). 

Maximum or Absolute natality - maximum offspring produced under most suitable environmental conditions. 

Ecological natality - refers to number of offspring produced under prevailing environmental conditions.

TLS Online TPP Program

#Id: 5516

#Unit 10. Ecological Principles

Mortality refers to death of individuals in a population. 

Minimum mortality rate, minimum death rate which occurs under ideal conditions of environment

Actual death rate is referred to as Ecological mortality.

TLS Online TPP Program

#Id: 5517

#Unit 10. Ecological Principles

Biotic potential / Intrinsic rate of natural increase (r) It is the inherent power of a population to grow and reproduce when environmental conditions are favorable, and resources are unlimited. 

TLS Online TPP Program

#Id: 5518

#Unit 10. Ecological Principles

Net reproductive rate, the average number of female offspring produced by all the females in a population over the course of a generation.