Ecology MCQ - IIT JAM MCQ

As we know, from long distance in forest it is impossible for these flies to recognize fruits for their food by the means like shape and color of the fruit. So, scent is the only possible way which can be utilized by these flies to localize their potential mates by localizing the fruits.

According to the optimal foraging theory, natural selection favours the individuals whose foraging behaviour provides them maximum energy with very little energy loss so that the net energy gained remains high.

As the prey population increases, the predator population also increases. As a result the prey population starts to decrease, which causes the predator population to decrease.

Dioecious is a plants species which have the male and female reproductive organs in separate individuals. For such kind of species allee effect will be more predominant because at low population density individuals of one sex also need to seek their potential mates.

As light wavelength decreases from red to blue light, so does the ability of light to penetrate water. Blue light penetrates best; green light is second, yellow light is third, followed by orange light and red light. Red light is quickly filtered from water as depth increases and red light effectively never reaches the deep ocean. So, red cannot be utilized by organism which is present in deeper zone of water. As we know light is a very important factor for distribution of photosynthetic aquatic organisms. And separate wavelengths of light reflect and absorb differentially in water.

Threatened species are any species which are vulnerable to endangerment in the near future.  Koala is a herbivorous marsupial native to Australia and was listed under the threatened species. Species in all other options are already extinct.

Parasitoids are a form of parasitic insects that lay their eggs inside or on living organisms. The larvae usually feed on the body of the host, often killing it.

The k-selected species are those whose populations fluctuate as they reach the carrying capacity. They represent stable populations, and have a few offsprings, lower fecundity, care for their young ones and have extended gestation periods. Only the r-selected species prefer the less crowded ecological niches where they can expand quickly in a short duration.

The two species of Paramecium show competitive exclusion when grown together because one species appears to use limited resources much more efficiently than the other, ultimately eliminating the other species.

The population is a group of individuals belonging to the same species, inhabiting the same area and interbreeding among themselves.

Density is defined as the number of individuals per unit area. Thus, the ecologist was comparing the density of squirrels in the two forests

These examples represent altruism which is the selflessness that some animals exhibit and kin selection which can be defined by the coefficient of relatedness or Hamilton’s rule where altruism is directed towards relatives.

Exponential growth is not a very sustainable form of growth as resources deplete faster in this case. It does not result in competition as all individuals can use the resources freely and there is no factor which limits their growth.

Habitat destruction and damage to bamboo plants on which pandas feed would limit the panda population severely.

When resources are scarce, animals may not gain enough energy to balance the energy needs used in defense. When resources are abundant, the animals need not spend any extra energy in the defense because resources are easily available. During the non-breeding season, animals need not add to the cost of defending a territory which they vigorously do during the breeding season for easy access to a mate.

Habitat fragmentation leads to increased edges or the boundaries which affect populations negatively. It leads to restricted gene flow between populations living in different patches after fragmentation which is detrimental to their growth. Small areas do not support a large population or animals which need a large area range to live.

Density dependent factors affecting a population are those factors which depend upon the number of individuals living in a specified area. Due to crowding, diseases spread easily, competition increases and rate of predation also increases. Factors such as natural calamities are density-independent and they can occur regardless of the number of individuals in an area.

The birth rate is more than the death rate so the population will increase by the rate 0.04–0.02 = 0.02.
The number of ants added will be 0.02×1000 = 20

Maximum population growth of a population happen at half of the carrying capacity.
So, at maximum population growth period the size of the population should be 400/2=200 individuals.
So, the formula for logistic population growth is  dN/dt= rN ( 1 – N/K)
dn/dt = 0.15 × 200 (1 – 200/400)
= 0.15 × 200 (0.5)
= 0.15 × 100
= 15 individuals per week

If we only consider birth rate in the population then there will a increase of 50 × 0.5 = 25 individuals in the total population. As the actual increase in the population is only 6 individuals, it means there is a death of 19 individual during this session.
So the death rate is, 50 × X = 19, X = 19/50 = 0.38

Formula for mark and recapture technique = N = (M×C) / R
N = estimated Number of individuals in the population
M = number of individuals captured and Marked
C = total number Captured the second time (with and without a mark)
R = number of individuals Recaptured (those with a mark)
So, N = 247 × 173/ 98
N = 436.03