BIOLOGY 2 Marks Questions

Law of Limiting Factors: Proposed by F.F. Blackman (1905), this law states that "if a chemical process is affected by more than one factor, then its rate would be determined by a factor that is nearest to its minimal value; it is the factor that directly affects process if its quantity is changed".

There are millions of living organisms in the world. Often, these organisms are known by their local names that vary from place to place, even within a country. Hence, the naming process of living organism is standardised in a way that a particular organism is known by the same name all over the world in the scientific community.

Hormones which do not enter the target cells, interact with specific receptors located on the surface of the target cell membranes and generates second messengers (e.g., cAMP) on the inner side of the plasma membrane. The second messenger, in turn, carries out all the hormonal functions.

Sense Organs in Frog:
Frog has different types of sense organs which are as follows:
(a) Sensory papillae or organs of touch,
(b) Taste buds.
(c) Nasal epithelium for the sense of smell,
(d) Eyes for vision and
(e) Tympanum with internal ears for hearing.
Out of these, eyes and internal ears are well-organised structures and the rest are cellular aggregations around nerve endings. Eyes in a frog are a pair of spherical structures situated in the orbit in skull. These are simple eyes. External ear is absent in frogs and only tympanum can be seen externally. The ear is an organ of hearing as well as balancing.

Functions of the ground tissue systems are as follows:
i. It provides mechanical strength while showing bending.
ii. It has spaces to allow gaseous exchange between cortex and atmosphere.
iii. It carries out photosynthesis.