An interesting modification of flower shape for insect pollination occurs in some orchids in which a male insect mistakes the pattern on the orchid flower for the female species and tries to copulate with it, thereby pollinating the flower. This phenomenon is called:
For its pollination the orchid Ophrys speculum has picked on the most selective attraction in the entire animal kingdom. It is pollinated by a hairy wasp, Colpa aurea. The wasp has a fixed habit whereby its males leave the burrows for above-ground existence about four weeks before the females emerge for the open-air mating. The orchid opens its flowers about the same time the males appear and they possess an appearance and odour similar to those possessed by the female wasps. The inexperienced males mistake the Ophrys flowers for their female counterparts and land to perform the act of pseudo-copulation. The insect repeats the act with a number of orchid flowers and carries pollinia from one flower to another. This insect-plant relationship is beneficial only to the plant.
Two opposite forces operate in the growth and development of every population. One of them relates to the ability to reproduce at a given rate. The force opposing to it is called
Mortality is the average number of natural deaths per unit population per unit time. Fecundity refers to the biotic potential of the organism. Environmental resistance is the sum total of all limiting factors that prevents a population to realize its full potential.
Which of the following communities is more vulnerable to invasion by outside animals and plants ?
This is so because oceanic islands are normally cut off from other habitats.
Which part of the world has a high density of organisms? 
Tropical rain forests occur in equatorial and subequatorial regions. The forests receive all the external inputs for optimum plant growth. Due to abundant plant growth, a large number of animals live in tropical rain forests. In grasslands fire occur periodically which prevent tree growth. In savannahs periods of drought are common. In deciduous forests are found predominantly broad leaved hard wood deciduous trees.
In a population unrestricted reproductive capacity is called as
Carrying capacity refers to the maximum number of individuals that can be sustained by the environment. Birth rate refers to number of births per unit population.
Choose the correct sequence of stages of growth curve for bacteria
The growth curve for bacteria is sigmoid. First phase is the phase of slow growth- Lag phase. Second phase is the period of accelerated growth - Log phase. Third phase is the phase when growth rate becomes stable - Stationary phase. Finally growth rate declines.
The semilog of per minute growing bacteria is plotted against time. What will be the shape of graph?
Semilog of per minute growing bacterium when plotted against time, would yield ascending straight line.
Two opposite forces operate in the growth and development of every population. One of them relates to the ability to reproduce at a given rate. The force opposing it is called
Biotic potential is the inherent ability of an organism to reproduce. Resistance refers to the sum total of all the limiting factors that inhibit further growth of population.
Diffuse porous woods are characteristic of plants growing in
Diffused porous wood have vessels irregularly arranged within the wood. In tropics, there is no sharp distinction between the seasons; hence, there is not much difference in the activity of cambium.
What is a keystone species ?
A keystone species is the one which makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community’s organization and survival.
In which one of the following habitats does the diurnal temperature of soil surface vary most?
Desert show maximum difference between day and night temperature.
The maximum growth rate occurs in
In the sigmoid growth cur ve growth is slow in the lag phase. Growth rate remains stable during the stationary phase and it declines during the senescent phase. Growth increases logarithmically during the exponential phase.
Certain characteristic demographic features of developing countries are
Demography is the study of population in all aspects. Fertility refers to the number of children per couple. Mortality rate is the average number of natural deaths per unit population per unit time. Age distribution refers to the proportionate occurrence of individuals of the three age groups. Developing countries usually have high rate of population growth, because of increasing fertility and declining mortality.
Niche overlap indicates
Niche indicate the habitat of a particular species and the interaction of that species with the resources present in the habitat. Niche overlap means that two or more species sharing the resources present in a particular niche.
The formula for exponential population growth is
The formula of exponential growth is is the rate of change in population size, r is the biotic potential and N is the population size.
Praying mantis is a good example of
Praying mantis is a good example of camouflage. Camouflage is the natural colouring of an animal which enables it to blend in with its surroundings.
A praying mantis, or praying mantid, is the common name for an insect of the order Mantodea. Often mistakenly spelled preying mantis (a tempting mistake, as they are notoriously predatory) they are in fact named for the typical “prayer-like” stance. The word mantis derives from the Greek word mantis for prophet or fortune teller. A praying mantis from India
Geometric representation of age structure is a characteristic of
Geometric representation of age structure a characteristic of population.
The population of an insect species shows an explosive increase in numbers during rainy season followed by its disappearance at the end of the season. What does this show?
If a population (e.g reindeer population) is allowed to grow in a predator free environment, the population grows beyond carrying capacity and there occurs population crash due to sudden shortage of food. Such growth curves also occur in insect populations during rainy season, and in algal blooms.
Two plants can be conclusively said to belong to the same species if they
When the members of a species are inter - fertile and produce fertile offsprings.
A high density of elephant population in an area can result in
It is competition between individuals of same species. The intraspecific competition may be very severe because all the members of a species have similar requirements of food, habitat mate, etc and they also have similar adaptations to get their needs.
What is true about the isolated small tribal populations?
There is a decline in population as boys marry girls only from their own tribe in the isolated small tribal populations.
In the case of peppered moth (Biston betularia) the black - coloured form became dominant over the light- coloured form in England during industrial revolution.
‘A’ is more recent and shows slight reduction in growth rate.
Large woody vines are more commonly found in :
Large woody vines are more commonly found in tropical rain forests. This is a common concern in the high humidity climatic condition.
Which one of the following statements is correct for secondary succession ?
Secondary succession refers to the regrowth of a habitat in the area where disruptive event has occurred and eliminated the existing, above ground plant life of the natural habitat. So, it occurs on a deforested site.
Cuscuta is an example of
Cuscuta, or Dodder plant, is a parasitic plant that wraps around other plants for nourishment. Cuscuta is found on outer side of the host and is total stem parasite. Cuscuta a parasite of Acacia.