The Living World Class 11 notes ( biology notes class 11 chapter 1 notes)

 Ernst Mayr:

1. Darwin of the 20th century.
2. Top 100 scientists of all time
3. Gave the currently accepted definition of species
4. He got three prizes called triple crown of biology

(a)  Balzan prize

(b) International prize for biology

(c)  Crafoord  prize

1. He died at the age of 100.  

Explanation: the scientist named Ernst Mayr is called one of the top 100 scientists that ever lived. Above are some things you should remember for the exam.

Question: What is the purpose of living?

Answer: It is a philosophical question and we do not discuss that in this chapter

Question: What is living?

Answer: A living organism is defined by some features that differentiate it from non-living inanimate matter.

Question: what are these features?

Answer: these features are (1) Growth

                                                   (2) Reproduction

                                                   (3) Metabolism

                                                   (4) Consciousness

Question: what is a feature?

Answer: A feature is a characteristic that is found in living organisms or nonliving matter.

Question: What is a defining feature?

Answer: A defining feature is a feature that is found in all living organisms and absent in all non living matter.

Question: Examples of defining features of living organisms.

Answer: metabolism and consciousness.

EXPLANATION: we do not discuss the purpose of living in this chapter because it is not a scientific question and has nothing to do with biology. We will try to define living organisms through a scientific method which is by differentiating them from non living organisms.

But how do we differentiate between the living and the non-living? One way to do it is by looking at the features and characteristics of living organisms and how they are different from those of non-living things.

Growth

Twin characteristic of growth: Increase in cell number & increase in mass.

Unicellular: Increase in size, Cell divide [single cell –Growth& Reproduction same].

Multicellular: Increase in size, Increase in number of cells.

Plant Growth: Unlimited, Meristematic(related to meristematic tissue).

Animal Growth: Limited, Uniform

Living being: intrinsic growth.

Non-living: extrinsic growth(deposition/accretion of material on the surface).

***Growth is not a defining feature.

Explanation: What is growth you might think? Well in biology increase in mass and increase in number means growth. Now, in unicellular organisms reproduction and growth is mutually exclusive. Mutually exclusive means if one thing happens then the other has to happen. What happens in the case of unicellular organisms is they grow by cell division. But they also reproduce by cell division, so it is the same for them. Growth and reproduction happen together. You get it right?

But in the case of multicellular organisms, it is different. Now I will give you an example to explain this. Let's say we have a puppy. A puppy is 1 organism. Now the puppy grows up. He goes through the process of Growth. The grown puppy is still 1 organism. Why? Because he went through the process of growth and not reproduction. Because growth and reproduction are not mutually exclusive in multi-cellular organisms. They don't need to happen at the same time. So what is the difference between the small puppy and the grown puppy? The grown puppy is bigger. How?

Cell division. The grown puppy has more number of cells. Because in multicellular organisms cell division does not mean reproduction.

--To summarize in unicellular organisms growth, cell division, and reproduction happen together.

-- in multicellular organism, they don't have to. They can happen separately.