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Organisms and Populations — BIOLOGY STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 ScienceBIOLOGYOrganisms and Populations4 Marks
Question
Explain Predation as population interaction with different example.
✓

Answer

→ In a broad ecological context, all carnivores, herbivores etc. are predators. About 25% insects are phytophagous.
→ If a predator overexploits its prey, then the prey might become extinct. It results in the extinction of predator. Therefore, predators in nature are 'prudent'.
Importance of predators :
→ Predators control prey populations.
→ When certain exotic species are introduced into a geographical area, they spread fast due to the absence of its natural predators.
E.g. Prickly pear cactus introduced into Australia (1920's) caused havoc by spreading. Later, it was controlled by introducing a cactus-feeding predator moth.
→ Predators are used in Biological control methods.
→ Predators maintain species diversity in a community by reducing competition among prey species.
E.g. the predator starfish Pisaster in the rocky intertidal communities of American Pacific Coast. In an experiment, all these starfishes were removed from an enclosed intertidal area. It caused extinction of over 10 invertebrate species within a year, due to interspecific competition.

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Similar questions

​​​​Read the following and answer any four questions from (i) to (v) given below:

Edward Wilson described diversity at all levels of biological organisation ranging from macromolecules inside the cells to biomes. It is of three inter-related hierarchial levels-genetic diversity, species diversity and conununity ecosystem diversity. Species diversity is the variety in the number and richness of the species of a region. For example, the Western ghats have a greater amphibian species diversity than the Eastern ghats.

  1. The number of species per unit area is called.
  1. Species evenness.
  2. Species richness.
  3. Species equitability.
  4. Both (a) and (c).
  1. The table below gives the population (in thousands) of ten species (A - J) in four areas (I - IV) consisting of the number of habitats given within brackets against each. Study the table and answer the question which follows:
Area and number of habitats
Species and their population (in thousands) in the area
A
B
C
D
E
F
G
H
I
J
I(11)
23
12
0.52
6.0
-
3.1
1.1
9.0
-
10.3
II(11)
10.2
-
0.62
-
1.5
3.0
-
8.2
1.1
11.2
III(13)
11.3
0.9
0.48
2.4
1.4
4.2
0.8
8.4
2.2
4.1
IV(12)
3.2
10.2
1.1
4.8
0.4
3.3
0.8
7.3
1.3
2.1
Which are out of I to IV shows maximum species diversity?

  1. II
  2. III
  3. IV
  4. I
  1. Study the given populations and choose the correct answer in relation to species diversity.
Population
Species
Species
Individuals
Population A
I
Mammals
3
II
Birds
2
III
Amphibians
2
Population B
I
Mammals
2
II
Mammals
2
III
Amphibians
1
Population C
I
Mammals
3
II
Mammals
2
III
Mammals
4

 

 
Maximum diversity
Minimum diversity
(a)
Population B
Population C
(b)
Population A
Population C
(c)
Population A
Population B
(d)
Population B
Population A
  1. The concept of species diversity has two components : evenness and richness. Evenness is based on the relative abundance of species. Richness is based on the total number of species present. Diversity indices combine a measure of richness and evenness. The Simpson index (D) is calculated from the following equations:

$\text{D}=\displaystyle\sum_{\text{i}=1}(\text{n}_\text{i}/\text{N})^2$

where, n = total number of organisms of particular species

N = total number of organisms of all species

Below are data collected in two terrestrial plant conununities that represent part of a successional chronosequence. ln this case the values were measured as percent cover.

Early Successional Community
Late Successional Community
Species
Percent Cover
Species
Percent Cover
A
83
F
24
B
5
G
20
C
9
H
18
D
2
I
23
E
1
J
15
The data indicate that, relative to the early successional community, the late successional community has which of the following characteristics?

 
Species Richness
Evenness
(a)
Higher
Higher
(b)
Higher
Lower
(c)
Same
Lower
(d)
Same
Higher
  1. Select the incorrect statement regarding species diversity.
  1. It results in polymorph formation and is useful in adaptation to changes in environmental conditions.
  2. Number of individuals of different species represent species evenness.
  3. It influences biotic interactions and stability of the community.
  4. It is a trait of the community.
→
Read the following and answer any four questions from (i) to (v) given below:

Aditya went to his hometown located in countryside along with his parents during his summer vacations. His grand parents' house is surrounded by farmland from all sides. Lots of crops were growing nearby and Aditya was very excited to visit the crop fields. He seeked permission from his mother to play in farmland along with his friends and then went to play in the fields. On returning back he had running nose, watering eyes and continuous sneezing which was very frequent. TI1e symptoms worsened with time. Based on the above information, answer the following questions.

  1. What could be the possible reason for Aditya's condition?
  1. Allergy
  2. Infection
  3. Malnutrition
  4. Genetic disorder
  1. How can allergy be diagnosed in a person?
  1. Presence of large amount of IgE antibodies in the blood.
  2. Presence of large number of bacteria in the blood.
  3. Presence of bilirubin and bilirubin pigments in the stool.
  4. Presence of sickle shaped RBCs in the blood
  1. The symptoms which Aditya developed on account of being allergic are consequence of?
  1. Inflammation of membrane lining the nose and conjunctiva
  2. Swelling up of tissue surrounding bronchioles of lungs
  3. Dilation of all arteries so that large amount of fluid passes from blood to tissues.
  4. All of these.
  1. Name the type of allergy that Aditya developed.
  1. Asthma
  2. Anaphylaxis
  3. Hay fever
  4. Urticaria
  1. Assertion : Hay fever is the form of allergy due to pollens of grasses and other plants.

Reason : Hay fever symptoms are due to release of histamines and often respond well to treatment with antihistamines.

  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
→
Read the following and answer any four questions from (i) to (v) given below:

When it comes to biopesticides, one of the most widely used fungi is Beauveria bassiana. It infects a range of insects like, pecan weevil, Colorado potato beetle, kudzu bug, etc. It causes a disease known as the white muscardine. Even after an insect is killed, the white mold continues to produce millions of new infective spores that are released into the environment. It is commercially formulated as products including Naturalis L, Mycotrol, BotaniGard, etc. Some other widely used molds are Trichoderma, Metarhizium, etc. Some of them release enzymes that dissolve potential pathogens, others form barriers around plant roots and make it impossible for harmful bacteria and pathogens to pass through.

  1. The key benefits of the biopesticides are that they are:
  1. Highly effective.
  2. Target specific.
  3. Reduced environmental risks.
  4. all of these.
  1. Naturalis-L is a conunercial formulation containing:
  1. Bacterial biopesticide.
  2. Fungal biopesticide.
  3. Fungal biofertiliser.
  4. Chemical pesticide.
  1. Which of the following is used as an effective bacterial biopesticide?
  1. Trichoderma.
  2. Beauveria.
  3. Bacillus thuringiensis.
  4. All of these.
  1. Baeuveria causes a disease called:
  1. White muscardine.
  2. Aspergillosis
  3. Green muscardine.
  4. Powdary mildews.
  1. Assertion: Trichoderma, found in root ecosystem, exerts biological control over several plant pathogens.

Reason: Trichoderma release enzyme which inhibits growth of several disease causing pathogens.

  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
→
Read the following and answer any four questions from (i) to (v) given below:
A group of teenagers was involved in drug abuse. 'They used syringes and needles to inject drugs. 'They indulged in this habit when they became adults. Administration of drug through needles became a piece of cake for them. Raj was the most active drug abuser amongst them and used to take drugs in high profile parties. In a span of time he started losing weight and suffered persistent diarrhoea. He developed constant low grade fever and used to catch opportunistic infection. When he consulted a doctor, he got himself tested for HIV in his blood and finally diagnosed with AIDS.
Based on the above information, answer the following questions.
  1. Select the incorrect statement.
  1. AIDS is a disorder of cell mediated immune system of the body.
  2. AIDS is caused by Human Immunodeficiency virus.
  3. AIDS infections were detected in India for the first time in prostitutes of Chennai, Tamil Nadu in 1986.
  4. December 10 is recalled as World AIDS Day.
  1. How do you think Raj got AIDS infection?
  1. Through transfusion of HIV infected blood
  2. Sexual intercourse with an infected partner
  3. Sharing towel with infected friend
  4. Use of contaminated needles and syringes to inject drugs
  1. How AIDS can be diagnosed?
  1. ELISA test
  2. Ames test
  3. Pap's test
  4. Wida! test
  1. How can AIDS be prevented?
  1. Blood tests of blood donor before transfusion to check for the presence of AIDS virus.
  2. Use of disposable needles and syringes for injecting medicines and vaccination
  3. Having protected sex by use of condoms
  4. All of these
  1. Select the correct statement for AIDS virus.
  1. It is rhomboid in shape with a diameter of 10-15 cm.
  2. Its genome consists of ds DNA.
  3. It consists of reverse transcriptase enzyme.
  4. Its envelope consists of lipid bilayer and three protein coats.
→
The bacterium Bacillus thuringiensis is widely used in contemporary biology as:
  1. Agent for production of dairy products.
  2. Source of industrial enzyme.
  3. Indicator of water pollution.
  4. Insecticide.
→
Describe tissue culture.
→
Read the following and answer any four questions from (i) to (v) given below:
In recombinant DNA technology, the fragments of DNA generated after cutting the DNA by restriction enzymes are separated according to their size or length by gel electrophoresis. Gel electrophoresis is performed in a gel matrix so that molecules of similar electric charges can be separated on the basis of size. Most commonly used matrix in gel electrophoresis is agarose. The fragments are separated under the influence of electric field. The separated DNA fragments can be seen only after staining the DNA with compound known as ethidium bromide (EtBr) followed by exposure to UV radiation as bright orange band.
  1. Gel electrophoresis is used for the separation of
  1. DNA only.
  2. DNA and RNA only.
  3. DNA and proteins only.
  4. DNA, RNA and proteins.
  1. Most commonly used matrix is _____ which is a ______ extracted from _______.
  1. (i) agarose (ii) polysaccharide (iii) sea weed
  2. (i) agarose (ii) protein (iii) sea weed
  3. (i) EtBr (ii) polysaccharide (iii) sea weed
  4. (i) EtBr (ii) protein (iii) bacteria
  1. A DNA molecule was treated with a restriction endonuclease and three fragments of size (i) 426kb, (ii) 129kb and (iii) 46kb were obtained. Identify the order in which these bands will arrange themselves in the gel plate after gel electrophoresis is completed. (Assuming that negative part of electrode is towards the well)
  1. (iii) → (ii) → (i)
  2. (i) → (ii) → (iii)
  3. (i) → (iii) → (ii)
  4. (iii) → (i) → (ii)
  1. Which of the following statements regarding gel electrophoresis is incorrect?
  1. Separated DNA fragments can be seen only after staining DNA with EtBr.
  2. DNA fragments are separated according to their size.
  3. Under the influence of electric field, positively charged molecules move towards the anode and negatively charged molecules move towards the cathode.
  4. None of these.
  1. The factor that will not affect the rate of DNA migration in gel electrophoresis is:
  1. Size of DNA molecule.
  2. Concentration of DNA.
  3. Voltage supplied.
  4. Concentration of the gel.
→
Read the following and answer any four questions from (i) to (v) given below:

Reerna, Jai and Ankit are suffering from autoimmune diseases of adrenal cortex, joints and thyroid gland, respectively. Their immune system failed to recognise self and non-self and started destroying their body's own proteins. They are seeking proper medical help for their conditions but their condition cannot be cured completely.

Based on the above information, answer the following questions.

  1. Select the option that correctly identifies autoimmune diseases of Reema, Jai and Ankit.
S no.
Reema
Jai
Ankit
(a)
Diabetes
Grave's disease
Rheumatic fever
(b)
Pernicious anaemia
Multiple sclerosis
Myasthenia gravis
(c)
Addison's disease
Rheumatoid arthritis
Hashismoto's thyroiditis
(d)
Systemic lupus erythematosus
Severe combined immunodeficiency disease
AIDS
  1. Reema's autoimmune condition is characterised by
  1. Undersecretion of insulin.
  2. Destruction of RB Cs and low RB C count.
  3. Undersecretion of adrenal cortex hormones.
  4. Low production of intrinsic factor required for absorption of B12
  1. What do you think is the major cause of Jai's condition?
  1. Deterioration of myelin sheath around nerve cells, leading to loss of precise muscle control
  2. Destruction of heart cells, leading to weakening of entire heart wall.
  3. Destruction of beta cells, leading to undersecretion of insulin.
  4. Deposition of immune complexes of IgM, IgG and complement in joints thereby inflaming joints, destroying articular cartilage and fusing bones.
  1. How do you think Ankit's condition got diagnosed?
  1. Low level of thyroid hormone and elevated levels of TSH in Ankit's blood.
  2. Presence of antibodies against thyroid pen oxidase (TPO antibodies) in Ankit's blood.
  3. Elevated erythrocyte sedimentation rate (ESR), reduced C-reactive protein (CRP) in Ankit.
  4. Both (a) and (b)
  1. Assertion: Immunosuppressive drugs often reduce the severity of autoimmune disorders.

Reason: Monoclonal antibodies have been successfully used in the treatment of autoimmune disease.

  1. Both assertion and reason are true, and reason is the correct explanation of assertion.
  2. Both assertion and reason are true, but reason is not the correct explanation of assertion.
  3. Assertion is true, but reason is false.
  4. Both assertion and reason are false.
→
Read the following and answer any four questions from (i) to (v) given below:

Ginkgo tree has been saved from extinction by selective breeding followed by channeling into trade of nature lovers. This is an ex-situ conservation, where endangered species are protected from all adverse factors. Offspring produced in captive breeding are released in natural habitat for acclimatisation.

  1. What is the significance of offsite collections?
  1. Restock depleted populations.
  2. Protection of endangered species.
  3. Reintroduce species in wild.
  4. All of these.
  1. Which of the following is not an ex-situ conservation?
  1. Wetlands
  2. Orchards
  3. Aquaria
  4. Botanical gardens.
  1. Select the incorrect statements for ex-situ conservation.
  1. It is conservation of species outside their natural habitats.
  2. Endangered species are kept under human supervision and provided all the essentials.
  3. The species population recovers in natural environment.
  4. Both (b) and (c).
  1. Conditions maintained in seed banks for orthodox seeds are:
  1. Low moisture content.
  2. Anaerobic conditions.
  3. Low temperature.
  4. All of these.
  1. Assertion: Animal species which have become extinct in wild continue to be maintained in zoological parks.

Reason: Captive breeding is the conservation of those cases where these is no realistic chance of in-situ survival.

  1. Both assertion and reason are true and reason is the correct explanation of assertion.
  2. Both assertion and reason are true but reason is not the correct explanation of assertion.
  3. Assertion is true but reason is false.
  4. Both assertion and reason are false.
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What is oogenesis? Give a brief account of oogenesis.###Define or Characterise: (i) Primary oocyte. (ii) Primary follicle. (iii) Secondary follicle. (iv) Tertiary follicle. (v) Antrum. (vi) Secondary oocyte. (vii) Graafian follicle.
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