BIOLOGY 3 Marks Question

Alien species invasion has been a threat to biodiversity. Example of Alien species invasion are as follows:
i. Nile Perch, introduced into lake Victoria (in East Africa), led to the extinction of Cichlid fish (more than 200 species) in the lake
ii. Introduction of African catfish (Clarias gariepinus), for aquaculture, posing threat to indigenous catfish
iii. Introduction of carrot grass (Parthenium) I Lantana I Water hyacinth (Eichhornia), which are invasive weed, that pose threat to native species or any other appropriate example.
Other Causes of biodiversity loss
i. Habitat loss and fragmentation
ii. Over exploitation
iii. Co-extinction

There are many wrong beliefs and misconceptions about the AIDS. AIDS cannot be acquired by the following activities:
i. Insect bites
ii. Crowded transport
iii. Shaking hands
iv. Sharing towels
v. Coughing and sneezing
vi. Kissing and embracing
vii. Sharing utilities and telephone
viii. Swimmingpools and toilets.

He used particular type of flasks in his experiment.
His flasks were pre-sterilised and heat-killed yeast culture was kept in them.
- One flask was kept closed and the other was left open.
- He showed that in the closed pre-sterilised flask, life did not come from the killed yeast, in the other flask that was kept open, life appeared from killed yeast. This dismissed the theory of spontaneous generation.
- He concluded that life can come from pre-existing life.

	In situ conservation		Ex situ conservation
1.	It means conservation on site. An endangered species is protected in its natural habitat by maintaining the habitat itself and defending the species from predators and poachers.	1.	It means off site conservation. An endangered species is protected by removing it from the threatened habitat and placing it under the care of humans.
2.	This approach emphasizes on the protection of total ecosystem.	2.	This approach restricts to the protection of genetic resources at population and species level.
3.	This approach includes methods of protection like establishing hot spots, national parks, wildlife sanctuaries and biosphere reserves.	3.	It is done through live collections of animals and plants in zoos, botanical gardens, seed banks, etc.

Gene therapy is a corrective therapy or technique of genetic engineering that is used to replace a faulty or non-functional gene with a normal healthy functional gene.
The first clinical gene therapy was given to a 4-year-old girl with ADA (Adenosine Deaminase) deficiency in 1900. It is caused due to the deletion of the gene coding for ADA, which adversely affects the functioning of the immune system.

→ Sigmoid curve
→ In nature a given habitat has enough resources to support a maximum possible number of population, beyond which no further growth of the population is possible. This limit is called as natures carrying capacity (K) for that species in that habitat.

Four symptoms of Down's syndrome are:
(a) feeble minded
(b) retarded growth
(c) rounded face and broad forehead
(d) permanently open mouth.
It is an autosomal aneuploidy or 21 trisomy. In this case the egg possesses 24 chromosome instead of 23 and the offspring has 47 chromosomes. (45+ XY in male, 445 + XX in female) instead of 46.

i. i-Regulatory gene, p-Promoter gene.
ii. The Inducer is lactose.
iii. Functions of Lactose
a. Enters the cell and binds to the repressor and inactivates it.
b. As a result, repressor cannot bind to the operator. This allows RNA polymerase to have access to the promoter and transcription proceeds.