Question
Explain loss of biodiversity.
✓
Answer
→ The biological wealth of our planet has been declining rapidly and the accusing finger is clearly pointing to human activities.
→ The colonisation of tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds.
→ The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years.
→Some examples of recent extinctions include the
→ Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller's Sea Cow (Russia) and three subspecies (Bali, Javan, Caspian) of tiger.
→ The last twenty years alone have witnessed the disappearance of 27 species.
→ Careful analysis of records shows that extinctions across taxa are not random; some groups like amphibians appear to be more vulnerable to extinction.
→ Adding to the grim scenario of extinctions is the fact that more than 15,500 species world- wide are facing the threat of extinction.
→ Presently, 12 per cent of all bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31per cent of all gymnosperm species in the world face the threat of extinction.
→ From a study of the history of life on earth through fossil records, shows that large-scale loss of species like the one we are currently witnessing have also happened earlier, even before humans appeared on the scene.
→ During long the period (> 3 billion years) since the origin and diversification of life on earth there were five episodes of mass extinction of species.
→ The difference is in the rates; the current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and our activities are responsible for the faster rates.
→ Ecologists warn that if the present trends. continue, nearly half of all the species on earth might be wiped out within the next 100 years.
→ The colonisation of tropical Pacific Islands by humans is said to have led to the extinction of more than 2,000 species of native birds.
→ The IUCN Red List (2004) documents the extinction of 784 species (including 338 vertebrates, 359 invertebrates and 87 plants) in the last 500 years.
→Some examples of recent extinctions include the
→ Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller's Sea Cow (Russia) and three subspecies (Bali, Javan, Caspian) of tiger.
→ The last twenty years alone have witnessed the disappearance of 27 species.
→ Careful analysis of records shows that extinctions across taxa are not random; some groups like amphibians appear to be more vulnerable to extinction.
→ Adding to the grim scenario of extinctions is the fact that more than 15,500 species world- wide are facing the threat of extinction.
→ Presently, 12 per cent of all bird species, 23 per cent of all mammal species, 32 per cent of all amphibian species and 31per cent of all gymnosperm species in the world face the threat of extinction.
→ From a study of the history of life on earth through fossil records, shows that large-scale loss of species like the one we are currently witnessing have also happened earlier, even before humans appeared on the scene.
→ During long the period (> 3 billion years) since the origin and diversification of life on earth there were five episodes of mass extinction of species.
→ The difference is in the rates; the current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and our activities are responsible for the faster rates.
→ Ecologists warn that if the present trends. continue, nearly half of all the species on earth might be wiped out within the next 100 years.
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Loss of habitat and fragmentation leads to loss in biodiversity. Explain with example.
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→- The first antibiotic was extracted from a:
- Lichen.
- Fungus.
- Eubacteria.
- Acti-nomycetes.
- Which of the following kills bacteria by interfering SOS ribosome function?
- Cephalosporin.
- Erythromycin.
- Streptomycin.
- Neomycin.
- $\beta$-lactum group of antibiotics kill the bacterial pathogen by:
- Disruption of plasma membrane.
- Inhibition of translation of mRNA.
- Inhibition of translation of mRNA
- Inhibition of transcription of mRNA.
- Penicillin is not used to treat.
- Pneumonia.
- Tonsilitis.
- Rheumatic fever.
- Candidiasis.
- Assertion: Cephalosporins act by disruption of bacterial cell wall synthesis mechanism.
Reason: Cephalosporins are bacteriostatic antibiotics.
- Both assertion and reason are true and reason is the correct explanation of assertion.
- Both assertion and reason are true but reason is not the correct explanation of assertion.
- Assertion is true but reason is false.
- Both assertion and reason are false.
Read the following and answer any four questions from (i) to (v) given below: Non-native or alien species are often introduced in advertently for their economic and other uses. They often become invasive and drive away the local species. Exotic species have proved harmful to both aquatic and terrestrial ecosystems. For example, water hyacinth (Eichhornia crassipes) was introduced in Indian waters to reduce pollution. It was clogged water bodies including wetlands at many places resulting in death of several aquatic plants and animals.
- Island water ecosystem are the most vulnerable due to:
- Small size.
- Small number of species.
- Increases reproductive capacity.
- Both (a) and (b).
- Which of the following is not an alien species?
- Lantana camara.
- Periplaneta americana.
- Nile Perch.
- Yucca moth.
- Second major cause of species extinction is:
- Habitat loss and fragmentation.
- Over exploitation.
- Alien species invasion.
- Co-extinction.
- Assertion: Eichhomia crassipes drains off oxygen from water and can be seen growing in standing water.
Reason: Eichhornia crassipes is an indigenous species of India.
- Both assertion and reason are true and reason is the correct explanation of assertion.
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What could be the possible reason for the decrease in the population of species P over a number of days?
- Species Q is a predator of species P.
- Species Q is a prey species which wiped out the population of species P.
- Species P and Q compete for space but feeds on different food.
- None of these.
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- Why do we still search for other alternatives to increase food production?
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The foundations of recombinant DNA (rDNA) were laid by the discovery of restriction enzymes. These enzymes are present in many bacterias where they function as a part of their defense mechanism called the Restriction Modification system (RM system). Molecular basis of this system was explained first by Werner Arber in 1962. The Restriction Modification system consists of two components:
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- It adds ethyl group to one or two bases usually within the sequence recognised by the restriction enzymes.
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- EcoR I
- BamH I
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In angiosperms, the pollen grains are being transferred from the anther to the stigma and is termed pollination. This phenomenon was first discovered by Camerarius (1694) in the end of seventeenth century. Pollen grains are immobile. They cannot reach the stigma by themselves. An external agent is required for this. The pollination is mainly of two types-self pollination and cross pollination. The diagram given below shows two plants of the same species showing different types of pollination.
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- Pollen.
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- Flowers of plants X and Y need to produce odour and nectar for completion of processes P and Q if they are entomophilous.
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| S. No | P | Q | R |
| (a) | Geitonogamy | Xenogamy | Autogamy |
| (b) | Allogamy | Chasmogamy | Cleistogamy |
| (c) | Autogamy | Geitonogamy | Xenogamy |
| (d) | Geitonogamy | Allogamy | Autogamy |
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- R.
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