Graphs are equally important for the preparation of NEET. Here, we bring to you a collection of all important graphs from biology chapters of classes 11 and 12 that are repeatedly asked in the entrance examination.
Table of Contents
- Class 11
- Chapter 13 – Photosynthesis in Higher Plants
- Graph 1 – Absorption Spectrum of Chl a, Chl b and Carotenoids
- Graph 2 – Action Spectrum of Photosynthesis
- Graph 3 – Action Spectrum of Photosynthesis Superimposed on the Absorption Spectrum of Pigments
- Graph 4 – Graph of Light Intensity on the Rate of Photosynthesis
- Chapter 15 – Plant Growth and Development
- Graph 5 – Arithmetic Growth
- Graph 6 – Geometric Growth
- Class 12
- Chapter 13 – Organisms and Populations
- Graph 7 – Biomes Distribution
- Graph 8 – Organismic Response
- Graph 9 – Population Growth Curve
- Chapter 15 – Biodiversity and Conservation
- Graph 10 – Species Area Relationship
- Chapter 16 – Environmental Issue
- Graph 11 – Sewage Discharge and BOD
Class 11
Chapter 13 – Photosynthesis in Higher Plants
Graph 1 – Absorption Spectrum of Chl a, Chl b and Carotenoids
A graph that tells us about how much energy the chlorophyll pigments are absorbing at different wavelengths of light (VIBGYOR) is known as the absorption spectrum. Plants consist of four important pigments, chlorophyll a, chlorophyll b, xanthophylls and carotenoids.
Inference from the Graph: This graph shows us that both chlorophyll a and chlorophyll b show highest absorption in blue-violet and red regions. Chlorophyll b shows higher absorption in the blue-violet region, whereas chlorophyll a shows higher absorption in the red region.
Graph 2 – Action Spectrum of Photosynthesis
The action spectrum of photosynthesis shows how the rate of photosynthesis varies with the wavelength of light.
Inference from the Graph: This graph tells us that the rate of photosynthesis is the highest in blue-violet and red regions on the visible spectrum of light.
Graph 3 – Action Spectrum of Photosynthesis Superimposed on the Absorption Spectrum of Pigments
Inference: This graph tells us that photosynthesis happens mostly at the blue-violet and red region of the light spectrum and chlorophyll a is the primary pigment required for photosynthesis.
Graph 4 – Graph of Light Intensity on the Rate of Photosynthesis
On plotting a graph of light intensity against rate of photosynthesis, a hyperbola is achieved.
Inference: Initially, on increasing the intensity of light, the rate of photosynthesis increases. But at 10% of incident sunlight, the rate of photosynthesis reaches saturation, and no further increase is observed.
Chapter 15 – Plant Growth and Development
Graph 5 – Arithmetic Growth
This graph shows the arithmetic growth of cells assuming that the resources are unlimited and thus giving a linear graph. This type of growth is not idealistic. In plants, this type of growth rate can be seen in meristematic tissue and is denoted by the following mathematical expression –
| Lt = rt + L0 |
Here, Lt = Length at time t
L0 = Length at time 0
r = Growth rate =
Graph 6 – Geometric Growth
Geometric growth is an idealistic growth pattern where it is assumed that the resources and nutrients are depleted after a point of time. In this type, a S-shaped or sigmoid curve is obtained which shows that growth stops eventually. This growth pattern is denoted by the following mathematical expression –
| W1 = W0ert |
Here, W1 = size at time t
W0 = initial size
r = growth rate
t = time of growth
e = base of natural logarithms
Class 12
Chapter 13 – Organisms and Populations
Graph 7 – Biomes Distribution
This graph is plotted for mean annual precipitation (which includes both rainfall and snow) against the mean annual temperature which gives the biomes distribution.
Inference: Taking examples from the graph, if we extrapolate the tropical forest point, the mean annual precipitation is around 400 cm and mean annual temperature is around 25 ℃. Such high precipitation and temperature is only observed in tropical forests.
Similarly, taking the point of the arctic and alpine tundra, we can observe that the mean annual precipitation is around 100 cm and mean annual temperature is ranging between -10 to 0℃. Such similar questions arise in biology NEET entrance exams where you will be asked to mark the regions in a graph based on the values in precipitation and temperature.
Graph 8 – Organismic Response
Organisms respond in three ways to their environmental conditions, they can either be regulators, conformers or partial regulators.
Regulators: Organisms such as us humans and other mammals are able to maintain their homeostasis such as body temperature and osmotic concentration by physiological and behavioural mechanisms.
Conformers: All plants and nearly all animals are conformers, which means they cannot maintain their homeostasis. They keep conforming to their ambient temperature and pressure and change their own temperature and osmotic concentration accordingly.
Partial Regulators: Squirrels are partial regulators that can regulate themselves to some extent but eventually conform according to the environment.
Graph 9 – Population Growth Curve
The above graph shows two growth models when the resources are unlimited and when the resources are limited.
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- Exponential Growth: The first curve is an exponential growth curve that is achieved when the resources are unlimited and hence is not an ideal case of growth. In a population of size N, the change in population density is denoted by the following mathematical expression –
Here, r is the intrinsic rate of natural increase,
N is the population size, and
is the change in population density.
- Logistic Growth: The second one is a logistic growth curve that shows an S-shaped or sigmoid curve assuming that the resources and space are limited. It is an idealistic growth curve. It depends on the carrying capacity (K) of the habitat which is the ability of the habitat to sustain a species up to a certain limit. The carrying capacity of a habitat should always be considered in limited resource conditions. The growth pattern can be denoted by the mathematical equation:
Chapter 15 – Biodiversity and Conservation
Graph 10 – Species Area Relationship
Alexander von Humboldt, a German naturalist and geographer explored the wilderness of South American jungles and observed that on increasing the area the species richness increases but it comes to a halt eventually and we achieve a rectangular hyperbola on the graph. It shows a linear graph when plotted on a log scale. Mathematical expression for both the curves are as below:
| S = CAZ |
| Log S = log C + Z log A |
Here, S = species richness,
A = area,
C = Y-intercept
Z = slope of the line (regression coefficient)
Ecologists have observed that the value of Z lies in the range of 0.1 – to 0.2 when considering a region but it increases to 0.6 – 1.2 when considering an entire continent.
Chapter 16 – Environmental Issue
Graph 11 – Sewage Discharge and BOD
Biological Oxygen Demand (BOD) is the amount of oxygen required by microorganisms to break down the organic materials discharged in a water body. This graph shows the relationship between sewage discharge and dissolved oxygen.
Inference: As the sewage is discharged in a water body, a sudden increase in the biological oxygen demand is observed because the microbes feed and decompose the organic matter that requires oxygen and multiply in number. To complete their oxygen demand, the microbes extract all the dissolved oxygen from the water body, and hence the concentration of oxygen in water becomes low. Once the process of decomposition is completed, the BOD becomes low and the dissolved oxygen reaches back to its normal position.
These are all the important graphs required for biology NEET 2023 preparation. Keep visiting BYJU’S for more information on NEET.
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