A yellow round seeded Pea plant is crossed with green wrinkled seeded Pea plant. Four phenotypes appeared in the progeny in the ratio of 1 : 1 : 1 : 1. The genotype of the two are YyRr and yyrr.

A cross is made between F1 individual and homozygous recessive individual is called Test cross.

A yellow round seeded plant (YyRr) is corssed with greed wrinkled seeded plant(yyrr). In the next generation, progeny with four types of phenotypes and genotypes are formed in 1:1:1:1 ratio. It is called Test cross.

The steps of sexual reproduction in plants are:-

Pollination-  the pollen grains are carried by wind, water or insects and animals to reach the stigma of the flower. This process of transfer of pollen grains is called pollination.

Germination-  the pollen tubes begins to grow towards the egg cell. These tubes are a pathway for the sperms or male gamete to reach the egg within the ovule.

Discharge of male gamete: The pollen tubes reach the ovule where it penetrates the ovule to reach the female gamete or egg.

Fertilization- the male gamete travel down the pollen tubes and fertilize an egg. In angiosperms, double fertilization takes place where both egg and the polar nuclei in the embryo sac are fertilized by the male gametes.

The inner walls of small intestine have thousands of finger-like outgrowths. These are called Villi.

The small little projections on the inner surface of the small intestine which help in absorbing the digested food are called villi. They are finger-like projection inside the small intestine to increase their surface area to absorb essential nutrients from the food. They have thin walls and mostly covered with a thin channel of blood capillaries so, the nutrients can be absorbed by blood and easily transport.

The growth movement in response to touch, or contact of a foreign body, in plants is called thigmotropism or thigmotropic movement. The stems and tendrils of the climbers are positively thigmotropic in their response. The coiling of garden pea tendrils around any support is an example of thigmotropism. Thigmonastic (haptonastic) movements are induced by some external stimuli. For example tentacles of Drosera leaf curve and the lamina lobes of Dionaea fold on coming in contact with an insect.

Australopithecus, (first Apeman): The early human stock gave rise to Australopithecus. It is the connecting link between apes and man.

Characteristics:

i. They were 1.5 m high and had human as well as ape characters.

ii. They had bipedal locomotion, an omnivorous diet, and had erect posture.

iii. Brain capacity 500cc, similar to that of an ape.

iv. They had a lumbar curve in the vertebral column and the pelvis was broad.

Peptide A and peptide B is linked by two disulfide linkages in insulin. Proinsulin is made up of 81 residues and formed by three distinct chains. The A chain, B chain, and the area connecting the two are named the C peptide. The correct structure of proinsulin is crucial for the correct folding of mature insulin, as the placement of the C peptide sets the molecule up to create correctly positioned disulfide bonds in and between the A and B chains.

W.G. Rosen coined the term 'Biodiversity'.

Biodiversity refers to diversity or variability of living organisms present on this planet earth and other species which have driven to extinction millions of years ago. The term Biodiversity is also referred to as the Biological diversity which principally indicates the total number of different living species, living within a particular region including the microbes, plants, animals, and ecosystems such as coral reefs, forests, rainforests, deserts etc.

Amnion of the mammalian embryo is derived from the ‘mesoderm' on the outer side and ‘ectoderm' on the inner side.The extraembryonic membranes consist of the Chorion (the combination of trophoblast plus underlying extraembryonic mesoderm), Amnion, Yolk sac, and Allantois.The amnion is a membrane that closely covers the embryo when first formed.It is filled with the amniotic fluid which causes the amnion to expand and become the amniotic sac which serves to provide a protective environment for the developing embryo or fetus.Chorion is formed from trophectoderm and mesoderm.Allantois and Yolk sac membranes have mesoderm on the outside and endoderm in the inner side.

Note:

• The Amniotic membrane is not part of the embryo itself but is derived from the tissues that emerged from the embryo.
• The amnion is found on the innermost part of the placenta. It lines the amniotic cavity and holds the amniotic fluid and the developing embryo.
• The chorion, on the other hand, is the outer membrane that surrounds the amnion, the embryo, and other membranes and entities in the womb.

Birth rate $=\frac{\mathrm{\Delta }\mathrm{N}}{\mathrm{N}\mathrm{\Delta }\mathrm{t}}$

Here, N=250
∆t=1 year 
∆N=2500−250
=2250

Birth rate $=\frac{2250}{250\times 1}$

=9