The dark patch of light is known as a shadow which is formed when there is an opaque object in the path of light.
When an image is the reflection of light. By seeing image, we can identify the object but shadow can mislead you from actual object.

Elbow and knee are not made up of a single bone rather they are made up of two or more bones which are joined to each other by a joint, i.e. hinge joint. This joint along with the muscles helps us to bend the elbow and knee.

The functions of a stem in a plant areas follows:
(i) It conducts water from roots to the leaves and other parts.
(ii) It conducts food from leaves to other parts of the plants.
(iii) It bears leaves, flowers and fruits.
(iv) It provides support to the plant.

The following adaptations are seen in the body of birds.
(i) Bones are hollow.
(ii) Forelimbs are modified into wings.
(iii) Body is streamlined.

Shadow of flying aeroplane cannot be seen on the earth because umbra region cannot able to reach the earth.

Bean stalk, gourd plants money and grapevines plants all have weak stem but readily climbs up a neighbouring support or a tree. These plants are called climbers.

No, all plants are of different sizes. According to their size, they are classified as herb, shrub and trees.

The veins of leaves and their type of venation are 

(a) In the given figure:
(i) Petiole (ii) Midrib (iii) Lamina (iv) Vein
(b) The leaf has reticulate venation, the veins in leaf occur in an irregular way forming a net-like structure.
(c) Grass leaves have parallel type of venation. The vein run parallel to each other on both sides of midrib.