List of top Questions asked in GATE Ecology and Evolution

A large forest area is fragmented into multiple smaller patches of different sizes. A researcher estimates the number of bird species in these forest fragments immediately following fragmentation, and then again 20 years later. The relationship between fragment size and species richness is shown in the graph for the two sampling events (immediately after fragmentation: closed circles and solid line; 20 years after fragmentation: open circles and dashed line). The best explanation for the differences in species richness with fragment size between the two sampling events is 

Soils undergo weathering over large time-scales (millions of years). Over time, concentration of phosphorus (P) declines monotonically (solid line), while nitrogen (N) shows a unimodal pattern (dotted line) as shown. 

Based on this pattern, which one of the following diagrams represents the likely trend in N:P ratio? 

Consider a population that shows logistic growth of the form 
\[ \frac{dN}{dt} = rN \left( 1 - \frac{N}{K} \right) \] where \(\frac{dN}{dt}\) is the population growth rate, \(r\) is the instantaneous rate of increase, \(K\) is the carrying capacity and \(N\) is the population size.
For such a population \((N > 0)\), which one of the following graphs shows the correct relationship between per capita growth rate \((\frac{1}{N} \frac{dN}{dt})\) on the y-axis, and population size (\(N\)) on the x-axis? 

Consider the following list of bacteria and the infections they cause in humans. 

Which one of the following combinations correctly matches these micro-organisms and the infections they cause in humans? 
 

In the graph shown, the solid line represents the best fit from an ordinary least-squares regression, where X is the predictor variable and Y is the response variable. In this case, which one of the following assumptions of the linear regression is violated?

In an island chain, species richness (S) increases with island area (A) according to the equation, $S = 4.3A^{0.55}$. Which one of the following graphs best represents this equation?
 

In a species of gecko, males are polymorphic such that some males are yellow and other males are white. A student hypothesises that body colour is a signal of aggression. To test this, he measures aggression in yellow and white males. He also measures body size in every individual he tests. He plots the data in the following way (yellow males: solid line and filled dots; white males: dashed line and open dots). Which one of the following statements is correct based on these data? 
 

A sample of heights of trees follows a normal distribution. In this sample, 68% of height measurements are expected to fall in the interval: \[ \text{mean} \pm \underline{\hspace{1cm}} \text{ standard deviation.} \] (Round off to the nearest integer.)

The probability of local extinction increases with body size when there is forest degradation, loss, and fragmentation. Consider the following hypotheses for the vulnerability of larger-bodied species: 

(P) Larger-bodied species tend to have smaller population sizes.
(Q) Larger-bodied species require larger territories/home ranges. 
(R) Larger-bodied species have higher absolute resource and energy requirements.

Which one of the following options correctly lists all potential reasons for the vulnerability of larger-bodied species? 
 

The frequency distributions of a trait in two populations, X and Y, are shown in the figure.

 

Which one of the following statements about the mean and standard deviation (SD) of the two populations is accurate?

Male beetles are of two phenotypes: horned and hornless. Horned males mate with twice as many females compared with hornless males. But females mated to hornless males produce one-third more offspring. The reproductive success of a male (number of offspring fathered) is the number of females he mates with multiplied by the number of offspring each female produces. The reproductive success of horned males is \(\underline{\hspace{1cm}}\) times that of hornless males. (Round off to one decimal place.)
A population shows exponential growth of the form \( N_t = N_0 e^{rt} \) where \( N_t \) is the population at time \( t \), \( N_0 \) is the initial population size, and \( r \) is the rate of increase. If \( r = 0.1 \), then the doubling time for this population is \(\underline{\hspace{1cm}}\) (Round off to two decimal places.)
At a locus with two alleles A1 and A2, the genotype A1A1 produces white flowers, A2A2 produces red flowers, and A1A2 produces pink flowers. For a population in Hardy-Weinberg equilibrium, the frequency of red flowers is 0.25. If the white-flowered plants are removed, and all pink and red flowered-plants in this population are randomly crossed amongst each other, the frequency of white flowered plants in the next generation will be \(\underline{\hspace{1cm}}\) (Round off to two decimal places.)
A gene duplication event in an organism results in two copies of a gene. Which one (or more) of the following outcomes is/are possible for the duplicated copy?
The egg-laying mammal, platypus, is known for its ability to inject venom by stabbing with spurs on its hindlimbs. Which one (or more) of the following statements supports the hypothesis that venom in this species is used for intrasexual competition?
Behavioural ecologists exploring a newly discovered island find 20 new species of terrestrial lizards. Males of these species have a dorsal ridge that varies in size from large in some species to entirely lacking in others. The scientists hypothesise that dorsal ridges in males evolved by runaway sexual selection stemming from sensory bias in females. Which one of the following would provide the necessary evidence to support this hypothesis?
Which one of the following represents the correct chronological order of geological periods (from oldest to most recent)?
Consider 1000 terrestrial species that have geographical ranges of different shapes and sizes. If the Earth were entirely covered by land (no oceans), and the ranges of these species were overlaid on the surface of the Earth at random, which one of the following patterns is expected?
A researcher measures the abundance of a tree species in 10 plots in each of two habitats. She tests for differences in abundance between the two habitats using an ANOVA. The results from the ANOVA are as follows: \[\begin{array}{rl} \bullet & \text{Mean abundance in habitat A = 30 trees} \\ \bullet & \text{Mean abundance in habitat B = 50 trees} \\ \bullet & \text{F-statistic (on 1 and 18 degrees of freedom) = 6.04} \\ \bullet & \text{P-value = 0.02} \\ \end{array}\] Here, a P-value of 0.02 means that:
Which one of the following statements is INCORRECT with respect to the tree of life?
A bird species has an annual survival probability of 0.30. While sampling the population of this species, the probability that any individual is captured in a given year is 0.40. A bird is captured, tagged, and released in Year one. The probability that it is re-captured in Year two is \(\underline{\hspace{0cm}}\) (Round off to two decimal places.)
Sex ratio at birth is biased towards females in a mongoose population. If the probability of having a daughter is 0.7 in this population, and if sex determination of each offspring is an independent event, then the probability that a female with a litter of four offspring has at least one son is \(\underline{\hspace{0cm}}\) (Round off to two decimal places.)
Homing pigeons can perceive the pattern of polarized light in the sky (which depends on the position of the sun relative to the earth). This enables homing pigeons to orient and navigate home if released in any location. One can reset their biological clock in captivity by artificially controlling the light conditions. If you acclimatize a pigeon to a new lighting cycle with "sunrise" at 6 PM and "sunset" at 6 AM, instead of 6 AM sunrise and 6 PM sunset that naturally occurs, the bird will be clock-shifted by 12 hours within a few days. Suppose you release two birds, a normal bird (N) and a 12-hr clock-adjusted bird (C), 30 km East of their home at 6 AM. In which direction will each bird fly?
Demographic stochasticity introduces random variation in population growth because
According to the MacArthur – Wilson equilibrium model of island biogeography, which one (or more) of the following factors affect(s) extinction rate on an island?