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Important Topics of Biology
(For College & All Types of Competitive Exams)
Following is a list of biology topics that have been carefully selected according to
their scope and importance
...
Moreover, questions frequently
arise from these topics in various competitive exams
...


1
...
Furthermore, all life on earth is directly or indirectly
dependent on this process
...


Complete Article of Photosynthesis
Photosynthesis is a process by which phototrophs convert light energy into
chemical energy, which is later used to fuel cellular activities
...

Photosynthesis definition states that the process exclusively takes place in the
chloroplasts through photosynthetic pigments such as chlorophyll a, chlorophyll
b, carotene and xanthophyll
...
The by-product of the photosynthesis process is oxygen
...


What Is Photosynthesis in Biology?
The word “photosynthesis” is derived from the Greek words phōs (pronounced:
“fos”) and σύνθεσις(pronounced: “synthesis“)Phōs means “light” and σύνθεσις
means, “combining together
...
”

Photosynthesis also applies to other organisms besides green plants
...
These organisms exhibit photosynthesis just like green plants
...
The by-product of this physio-chemical process is oxygen
...
Oxygen is liberated as a by-product and light is considered as a
major factor to complete the process of photosynthesis
...
Leaves contain microscopic
cellular organelles known as chloroplasts
...

Light energy is absorbed by chlorophyll molecules whereas carbon dioxide
and oxygen enter through the tiny pores of stomata located in the
epidermis of leaves
...

 These sugars are then sent to the roots, stems, leaves, fruits, flowers, and
seeds
...
These sugar molecules then combine
with each other to form more complex carbohydrates like cellulose and
starch
...


Where Does This Process Occur?
Chloroplasts are the sites of photosynthesis in plants and blue-green algae
...
These cell organelles are
present only in plant cells and are located within the mesophyll cells of leaves
...

On the other hand, low light intensity results in a lower rate of photosynthesis
...
Usually, carbon dioxide in the range of 300
– 400 PPM is adequate for photosynthesis
...

Water: As water is an important factor in photosynthesis, its deficiency can lead
to problems in the intake of carbon dioxide
...

Pollution: Industrial pollutants and other particulates may settle on the leaf
surface
...


Photosynthesis Equation
Photosynthesis reaction involves two reactants, carbon dioxide and water
...
Hence, the
photosynthesis reaction is considered to be an endothermic reaction
...
Such bacteria are called oxygenic
photosynthetic bacteria
...


Photosynthetic Pigments
There are four different types of pigments present in leaves:

Chlorophyll a
Chlorophyll b
Xanthophylls
Carotenoids
Structure of Chlorophyll

The structure of Chlorophyll consists of 4 nitrogen atoms that surround a
magnesium atom
...
Pictured above is chlorophyllf, which is more effective in near-infrared light than chlorophyll-a Chlorophyll is a
green pigment found in the chloroplasts of the plant cell and in the mesosomes of
cyanobacteria
...
Chlorophyll is
a mixture of chlorophyll-a and chlorophyll-b
...


Process of Photosynthesis
At the cellular level, the photosynthesis process takes place in cell organelles called
chloroplasts
...
As already stated, photosynthesis occurs in the leaves and the specialized
cell organelles responsible for this process is called the chloroplast
...
The lamina is used for absorption
of sunlight and carbon dioxide during photosynthesis
...
Chlorophyll absorbs the light energy
from the sun to split water molecules into hydrogen and oxygen
...
Furthermore, oxygen is liberated
out into the atmosphere through the leaves as a waste product
...

 Pigments are other fundamental cellular components of photosynthesis
...
All green plants
mainly contain chlorophyll a, chlorophyll b and carotenoids which are
present in the thylakoids of chloroplasts
...
Chlorophyll-a is the main pigment
...


Light Reaction of Photosynthesis (or) Light-dependent
Reaction
 Photosynthesis begins with the light reaction which is carried out only
during the day in the presence of sunlight
...

 The Grana, membrane-bound sacs like structures present inside the
thylakoid functions by gathering light and is called photosystems
...

 There are two types of photosystems: photosystem I and photosystem II
...

 During the light reactions, ATP and NADPH are generated by two electrontransport chains, water is used and oxygen is produced
...

 It is a light-independent process in which sugar molecules are formed from
the water and carbon dioxide molecules
...

 Plants capture the carbon dioxide from the atmosphere through stomata
and proceed to the Calvin photosynthesis cycle
...


The chemical equation for the dark reaction can be reduced to:

3CO2 + 6 NADPH + 5H2O + 9ATP → G3P + 2H+ + 6 NADP+ + 9 ADP + 8 Pi

Importance of Photosynthesis
 Photosynthesis is essential for the existence of all life on earth
...

 Photosynthesis is also responsible for the production of oxygen – which is
needed by most organisms for their survival
...
What is Photosynthesis? Explain the process of photosynthesis
...
The process of photosynthesis requires solar energy, water
and carbon dioxide
...

2
...

3
...

There are several factors that affect the rate of photosynthesis
...

4
...
Light-dependent reactions are also called light
reactions and occur during the day time
...

5
...
The complete
process of the Calvin cycle takes place in the stroma of the chloroplasts
...
Write down the Photosynthesis Equation
...
Carbon Cycle
The carbon cycle is a biogeochemical process that also has a significant impact on
life
...

The carbon cycle shows the movement of carbon in elemental and combined states
on earth
...


Carbon Cycle Definition
The carbon cycle is the process where carbon compounds are interchanged
among the biosphere, geosphere, pedosphere, hydrosphere, and atmosphere of
the earth
...

 These plants are then consumed by animals and carbon gets
bioaccumulated into their bodies
...

 Some of the carbon that is not released back into the atmosphere
eventually become fossil fuels
...


Carbon Cycle Diagram
The carbon cycle diagram below elaborates the flow of carbon along different
paths
...
Carbon enters
the atmosphere through natural processes such as respiration and industrial
applications such as burning fossil fuels
...
The equation is as follows:

CO2 + H2O + energy → (CH2O)n +O2

Carbon compounds are passed along the food chain from the producers to
consumers
...
The role of decomposers is to eat the dead organism
and return the carbon from their body back into the atmosphere
...
Ecologically, oceans take in
more carbon than it gives out
...
” Marine animals
convert carbon to calcium carbonate and this forms the raw building materials
require to create hard shells, similar to the ones found in clams and oysters
...
These accumulate on the seafloor and are eventually
broken down by the waves and compacted under enormous pressure, forming
limestone
...


Importance of Carbon Cycle
Even though carbon dioxide is found in small traces in the atmosphere, it plays a
vital role in balancing the energy and traps the long-wave radiations from the sun
...
If the carbon cycle is disturbed it
will result in serious consequences such as climatic changes and global warming
...
From proteins and
lipids to even our DNA
...

Hence, the carbon cycle, along with the nitrogen cycle and oxygen cycle, plays a
vital role in the existence of life on earth
...

 Carbon is an important element of life
...
Carbon atoms are then released as carbon
dioxide when organisms respire
...

 The carbon cycle is associated with the availability of other compounds as
well
...

The carbon cycle is a biogeochemical cycle where various carbon compounds are
interchanged among the various layers of the earth, namely, the biosphere,
geosphere, pedosphere, hydrosphere, and atmosphere
...


What are the types of the carbon cycle?
The carbon cycle can be classified into two types based on the duration of the
process into two types:
Short term – This type occurs within a relatively short period of time
...

Long-term – This type takes thousands of years to occur
...

Why is the carbon cycle important?
The carbon cycle is an important aspect of the survival of all life on earth
...

From a biological perspective, carbon is the building block of life and forms stable
bonds with other elements necessary for life
...
Nitrogen Cycle
Nitrogen is an important element required for life
...

This set of processes contributes to the nitrogen cycle
...
In this article, we shall
explore its implications on the environment in detail
...
”
Furthermore, nitrogen is a key nutrient element for plants
...
Read on
to explore how the Nitrogen cycle makes usable nitrogen available to plants and
other living organisms
...
It involves several processes such as
nitrogen fixation, nitrification, denitrification, decay, and putrefaction
...
Organic nitrogen exists in living
organisms, and they get passed through the food chain by the consumption of
other living organisms
...
This nitrogen is made available to plants by symbiotic bacteria which
can convert the inert nitrogen into a usable form – such as nitrites and nitrates
...
Furthermore, this process extends to various biomes, with the marine
nitrogen cycle being one of the most complicated biogeochemical cycles
...
These processes
take place in several stages and are explained below:

Nitrogen Fixation Process
It is the initial step of the nitrogen cycle
...
During the process of Nitrogen fixation, the inert form of nitrogen gas is
deposited into soils from the atmosphere and surface waters, mainly through
precipitation
...
Azotobacter and Rhizobium also have a
major role in this process
...

Nitrogen fixation can occur either by atmospheric fixation- which involves
lightening, or industrial fixation by manufacturing ammonia under high
temperature and pressure conditions
...


Types of Nitrogen Fixation

Atmospheric fixation: A natural phenomenon where the energy of lightning
breaks the nitrogen into nitrogen oxides, which are then used by plants
...
Ammonia is produced by the direct combination
of nitrogen and hydrogen
...

Biological nitrogen fixation: We already know that nitrogen is not used directly
from the air by plants and animals
...
These nitrogen compounds get fixed in the soil by these microbes
...
Nitrites are formed by the oxidation of ammonia with the help of
Nitrosomonas bacteria species
...
This conversion is very important as ammonia gas is toxic
for plants
...
This way, it enters the food web when the primary consumers eat the
plants
...
The decomposers, namely bacteria or fungi present in the soil,

convert the organic matter back into ammonium
...


Denitrification
Denitrification is the process in which the nitrogen compounds make their way back
into the atmosphere by converting nitrate (NO3-) into gaseous nitrogen (N)
...

Denitrification is carried out by the denitrifying bacterial species- Clostridium and
Pseudomonas, which will process nitrate to gain oxygen and gives out free nitrogen
gas as a byproduct
...
The only difference is that it is carried
out by marine bacteria
...
Due to
the geological uplift, these sedimentary rocks move to land
...
But, recent researches have proved that the nitrogen from these rocks is
released into the plants due to the weathering of rocks
...

 Helps in converting inert nitrogen gas into a usable form for the plants
through the biochemical process
...

 Nitrates and nitrites are released into the soil, which helps in enriching the
soil with the necessary nutrients required for cultivation
...

Nitrogen is also cycled by human activities such as the combustion of fuels and the
use of nitrogen fertilizers
...
The fertilizers containing nitrogen are
washed away in lakes, and rivers and result in eutrophication
...

 Nitrogen-fixing bacteria play a crucial role in fixing atmospheric nitrogen
into nitrogen compounds that can be used by plants
...
Then, these nitrogen compounds are used for the production of
proteins and other compounds in the plant cell
...
Humans consume proteins from these plants and
animals
...

 During the final stages of the nitrogen cycle, bacteria and fungi help
decompose organic matter, where the nitrogenous compounds get
dissolved into the soil which is again used by the plants
...
Eventually, it goes back to the atmosphere
...


Frequently Asked Questions
Why is nitrogen important for life?
Nitrogen constitutes many cellular components and is essential in many biological
processes
...

Why do plants need nitrogen?

Plants need nitrogen as this element is an important component of chlorophyll
...







Nitrogen Fixation
Assimilation
Ammonification
Nitrification
Denitrification

What is Ammonification?
Ammonification occurs during the decomposition of organic matter, where
ammonifying bacteria convert organic nitrogen into inorganic components like
ammonia or ammonium ions
...
Initially,
the ammonia is converted to nitrite (NO2−) by the bacteria Nitrosomonas, or
Nitrococcus, etc
...

What is Denitrification?
Denitrification is the process of converting the nitrate back into molecular
nitrogen by bacterias such as Pseudomonas, Thiobacillus, Bacillus subtilis etc
...

Which part of the plant is involved in nitrogen fixation?
The process of nitrogen fixation is carried out naturally in the soil within nodules
in the plant’s root systems
...
Difference between Mitosis and Meiosis
Mitosis and meiosis are two types of cell divisions that are observed in living
organisms
...


Meiosis
Meiosis is a type of cell division that results in the formation of four daughter cells
each with half the number of chromosomes as the parent cell
...


Introduction
In single-celled organisms, cell reproduction gives rise to the next generation
...

Cell division is always highly regulated and follows a highly orchestrated series of
steps
...
Mitosis results in two
nuclei that are identical to the original nucleus
...
In
animals, meiosis only occurs in the cells that give rise to the sex cells (gametes), i
...
,
the egg and the sperm
...

 Mitosis involves four basic phases – prophase, metaphase, anaphase and
telophase
...

 In mitosis, the nuclear membrane is broken down, spindle fibres
(microtubules) attach to the chromatids at the centromere and pull apart
the chromatids
...

 Each nucleus is identical to the original nucleus as it was in G1 phase
...

 In organisms that are diploid, the end result is cells that are haploid
...
e
...

 In humans, this means the chromosome number is reduced from 46 to 23
...

 The joining together of a sperm and egg during fertilisation returns the
number of the chromosomes to 46
...

 Meiosis consists of meiosis I and meiosis II
...

 This is the reduction division; chromosome number is divided in half
...


 As in mitosis, it is spindle fibers that “pull” the chromosomes and
chromatids apart in meiosis
...


Similarities between Mitosis and Meiosis
 Both mitosis and meiosis take place in the cell nuclei, which can be
observed under a microscope
...

 Both the processes occur in the M-phase of the cell cycle
...

 In both cycles, synthesis of DNA takes place
...
They are two very
different processes that have two different functions
...
Mitosis, on the other hand,
is focused on the growth and development of cells
...


Frequently Asked Questions
1
...

2
...

3
...

 Cytokinesis occurs only in telophase during mitosis, while it occurs in
Telophase 1 and telophase 2 during meiosis
...
It is also used
for cell reproduction
...
Tetrad formation is observed in
meiosis
...

 Asexual mode of reproduction is observed for mitosis
...

4
...

The similarities between mitosis and meiosis are as follows:





Mitosis and meiosis take place in the cell nuclei
...

Both the processes occur in the M-phase of the cell cycle
...

 Synthesis of DNA occurs in both
...
Flora and Fauna
Flora refers to all plant life while fauna refers to all animal life
...
7
million species of living organisms identified to date and more being discovered
every day
...


Introduction to Flora and Fauna

The ecosystem is a complex, interconnected network comprising biotic and abiotic
elements
...
Abiotic components, on the other hand, include non-living entities
that are vital for the survival of life and these include soil, water, climate, etc
...

Let us have a detailed look at the flora and fauna meaning and their importance
...
Let us dive deeper into these terms, exploring their origins and
etymologies
...
” Flora is a collective term for
a group of plant life found in a particular region
...
Flora is classified and differentiated based on many
factors
...

Some grow in desert regions or in water, some are found in hilly areas while some
are endemic to a specific geographic location
...
For example, Cactus plants are naturally seen in

deserts
...
The agricultural flora consists of plants
cultivated by men for their use
...


Fauna Meaning
Fauna represents the animal life indigenous to a region
...
As per Roman mythology, Fauna or
“Faunus” is the name of the goddess of fertility
...
“
The animal kingdom comprises a variety of animal life forms
...
Therefore,
for ease of classification;
 Birds are categorized under the name Avifauna
...

 Microorganisms including bacteria and virus are generally considered under
the animal kingdom, they are known as Microfauna
...

Since time immemorial, there have been accounts of animals that have been
thought to exist but have eluded the scientific community, thereby classifying them
as cryptofauna or cryptids
...
One such example is the colossal squid
...
It wasn’t until the 21st century when conclusive proof was
found in the form of a live specimen being entangled in a fishing net
...
Since
then, there has been undisputed confirmation about the existence of giant squids
...
Other life forms depend on
them for various resources and exploit them
...
Biosphere
reserves, national parks, zoos, and sanctuaries are a few instances of the measures
taken by the government for the conservation of flora and fauna
...


Importance of Flora and Fauna
The flora and fauna are important for the following reasons:

Maintains Ecological Balance
Flora and fauna are very important for human existence
...
Fauna, in turn, liberates
carbon dioxide consumed by the flora for photosynthesis
...
Animals maintain the
equilibrium by predating on different plants and animals to balance their
population on earth
...
The dead animals
decay and act as supplement minerals for other animals
...
People visit several biosphere reserves, national parks and zoos, forests,
botanical gardens, etc to enjoy the beauty of landmarks
...


Expansion of Local Economies
Flora and Fauna contribute to the local economies through tourism
...
Caribbean, Indonesia, Panama are
other tourist locations that attract millions of people due to its widespread flora
and fauna
...
It is naturally occurring or
the indigenous native plant life
...
These are the naturally occurring animal species of the particular
area
...
Fauna cannot
prepare their own food so they depend upon the flora for their food
...
Besides, the ecosystem becomes imbalanced if there are
any adverse effects on flora and fauna, such as an extinction of a species
...

Flora and fauna of India include a wide range of plant and animal species, most of
which is not found anywhere else in the world
...
Examples of fauna present in India include the Bengal tiger, Asian
elephant, snow leopard, Indian rhino, Indian sloth bear, etc
...
They
attract many tourists
...

Give some examples of flora and fauna
...

A few examples of fauna include- birds, animals, fish, insects, etc
...
Human Digestive System
Digestion is an important life process and is observed in a multitude of life forms
...

Unsurprisingly, humans have a digestive system too, and it is much more advanced
with a host of organs and glands that perform very specific functions and roles
...
Anatomically, the digestive
system is made up of the gastrointestinal tract, along with accessory organs such
as the liver, pancreas and gallbladder
...
Human Digestive
System and Nutrition involve the intake of food by an organism and its utilization
for energy
...
The food which we eat undergoes much processing before
the nutrients present in them are utilized to generate energy
...
Humans and other animals have specialized organs and
systems for this process
...
In humans, the process is quite
simple due to our monogastric nature
...
Some parts
of nervous and circulatory systems also play a significant role in the digestion
process
...

Let us have a detailed look at the human digestive system, its parts and functions
...


Parts of the Human Digestive System
The digestive system of the human body comprises a group of organs that work
together in converting food into energy and other basic nutrients to power the
body
...


The digestive system of the human body is the sum of the gastrointestinal tract
(GIT; also called alimentary canal) and accessory organs (tongue, liver, pancreas,
etc
...
The alimentary canal
is the long tube through which the food that we eat is passed
...
The
food particles gradually get digested as they travel through various compartments
of the alimentary canal
...
They stimulate the digestion by
releasing certain enzymes that help in breaking down the food
...
There are many other
organs that contribute to the digestion process, including teeth, salivary glands,
and tongue
...


Pharynx
A fibromuscular y-shaped tube attached to the terminal end of the mouth
...
It also has a major part in the respiratory system, as air travels
through the pharynx from the nasal cavity on its way to the lungs
...
It supplies swallowed food along with its
length
...
This vital organ acts as a storage for the food and
provides enough time to digest meals
...

Mucous: It is an aqueous secretion produced by the mucous membranes
...

Digestive enzymes: They are the group of enzymes that functions by breaking
down polymeric macromolecules like biopolymers into their smaller and simpler
substances
...
It functions by destroying harmful microorganisms present in the food
particles
...
It is present just behind the stomach and acquires a
maximum area of the abdominal cavity
...


Large Intestine
This is a thick, long tube measuring around 5 feet in length
...
It absorbs water and consists of bacteria (symbiotic) that support the
breakdown of wastes to fetch small nutrients
...
It is stored in the rectum
as semi-solid faeces which later exits from the body through the anal canal through
the process of defecation
...
It is short with its anterior
connected to the duodenum and posterior pointing towards the left part of the
abdominal cavity
...

Liver
The liver is a roughly triangular, reddish-brown accessory organ of the digestive
system located to the right of the stomach
...
The bile is stored and recycled in the
gallbladder
...


Digestion Process
The process of digestion begins from the mouth and ends in the small intestine –
the large intestines’ main function is to absorb the remaining water from the
undigested food and enable bacterial fermentation of materials that can no
longer be digested
...
Food
particles gradually get digested as they travel through various compartments of the
gastrointestinal tract
...


Ingestion
The very first step involves mastication (chewing)
...


Mixing and Movement
It involves the process of lubricating and manipulating food and pushing it down
the food through the food pipe (using peristalsis), and into the stomach
...
It functions by breaking down food particles into simple
components and easily absorbable components
...


Absorption
This process begins in the small intestine where most of the nutrients and minerals
are absorbed
...


Excretion
The process of removing indigestible substances and waste by-products from the
body through the process of defecation
...


Diarrhea: It is an abnormal watery bowel movement
...

Constipation: A condition in which the feces are clutched within the rectum due
to an irregular bowel movement
...
Indigestion is mainly caused

due to inadequate enzyme secretion, food poisoning, anxiety, overeating, and
eating spicy foods
...

Digestion is necessary for breaking down food particles into nutrients that are
used by the body as an energy source, cell repair, and growth
...
The body breaks the
nutrients present in the drinks and food into carbohydrates, vitamins, fats and
proteins
...

 The process of digestion takes place in 6 major steps
...

 The autonomous nervous system controls the peristalsis, contraction, and
relaxation of muscles within the alimentary canal wall
...

 Water, electrolytes and vitamins are absorbed by the large intestine and
the waste is defecated
...

The digestive system consists of the alimentary canal and the accessory organs
...

What are accessory organs?
Accessory organs are organs which are not part of the digestive system; however,
they aid in the digestion process by performing many secondary functions
...

Outline the process of digestion, step by step
...








Mouth & Buccal Cavity
Pharynx
Oesophagus
Stomach
Small Intestine
Rectum

Explain the role of the tongue as an accessory organ
...
Furthermore,
moistening food also helps to swallow and pass through the oesophagus without
much resistance
...
Human Heart
The heart is an important organ usually found in humans & animals
...
However, unlike
the invertebrates, the human heart is quite advanced with respect to its
structure, functions and capabilities
...
It is a muscular organ with four chambers
...
The human heart functions throughout a person’s lifespan
and is one of the most robust and hardest working muscles in the human body
...
Even invertebrates such as grasshoppers possess a heart
like pumping organ, though they do not function the same way a human heart does
...
It is derived from the embryonic
mesodermal germ layer
...
This replenishes oxygen and circulates nutrients among the
cells and tissues
...

 Blood delivers oxygen, hormones, glucose, and other components to
various parts of the body, including the human heart
...


Types of Circulation
Pulmonary circulation is a portion of circulation responsible for carrying
deoxygenated blood away from the heart, to the lungs and then bringing
oxygenated blood back to the heart
...
Now, the heart itself is a
muscle, and therefore, it needs a constant supply of oxygenated blood
...

Coronary circulation is an essential portion of the circulation, where oxygenated
blood is supplied to the heart
...

Moreover, organs like the brain need a steady flow of fresh, oxygenated blood to
ensure functionality
...
Let us
gain a deeper insight into the various anatomical structures of the heart:

Structure of the Human Heart
The human heart is about the size of a human fist and is divided into four
chambers, namely two ventricles and two atria
...
Among
these both the right atrium and ventricle make up the “right heart,” and the left
atrium and ventricle make up the “left heart
...


The right and the left region of the heart are separated by a wall of muscle called
the septum
...
The right semilunar valves close and prevent the
blood from flowing back into the heart
...
Read on to explore more
about the structure of the heart
...


Pericardium
The human heart is situated to the left of the chest and is enclosed within a fluidfilled cavity described as the pericardial cavity
...

The pericardium is a fiber membrane found as an external covering around the
heart
...
Apart from the
lubrication, the pericardium also helps by holding the heart in its position and by
maintaining a hollow space for the heart to expand itself when it is full
...

Parietal Layer: It forms a sac around the outer region of the heart that contains
the fluid in the pericardial cavity
...
It is composed of a
thin-layered membrane that serves to lubricate and protect the outer section
...
It contributes to the thickness and is responsible for the
pumping action
...
Furthermore, it prevents the blood from sticking to the
inner walls, thereby preventing potentially fatal blood clots
...
It is composed of a
thin-layered membrane that serves to lubricate and protect the outer section
...
It contributes to the thickness and is responsible for the
pumping action
...
Furthermore, it prevents the blood from sticking to the
inner walls, thereby preventing potentially fatal blood clots
...


Chambers of the Heart
Vertebrate hearts can be classified based on the number of chambers present
...
Avian and mammalian hearts consists of four chambers
...
These
are the blood-receiving chambers that are fed by the large veins
...
These are connected to larger arteries that
deliver blood for circulation
...
The walls consist of fewer muscles compared to the left portion, and
the size difference is based on their functions
...


Blood Vessels
In organisms with closed circulatory systems, the blood flows within vessels of
varying sizes
...

The external structure of the heart has many blood vessels that form a network,
with other major vessels emerging from within the structure
...

 Capillaries are tiny, tube-like vessels that form a network between the
arteries to veins
...
Aorta
is the largest of the arteries and it branches off into various smaller arteries
throughout the body
...
They ensure that the blood flows in a single direction (unidirectional)
...
Based on their function, valves are
of two types:
 Atrioventricular valves are between ventricles and atria
...


 Semilunar valves are located between the left ventricle and the aorta
...


Facts about Human Heart

 The heart pumps around 6,000-7,500 liters of blood in a day throughout
the body
...

 On average, the heart beats about 100,000 times a day, i
...
, around 3
billion beats in a lifetime
...

In females, it weighs around 230 to 280 grams (8 to 10 ounces)
...


Frequently Asked Questions
1
...

Pulmonary circulation is a type of blood circulation responsible for carrying
deoxygenated blood away from the heart, and to the lungs, where it is oxygenated
...


2
...

In systemic circulation, the heart pumps the oxygenated blood through the arteries
to every organ and tissue in the body, and then back again to the heart through a
system of veins
...
Elaborate on coronary circulation and its significance
...
This is where coronary circulation fulfills this function through
a network of arteries and veins in the heart
...

The human heart is divided into four chambers, namely
4
...

The human heart is divided into four chambers, namely two ventricles and two
atria
...
Among these, the right atrium and ventricle make
up the “right portion of the heart”, and the left atrium and ventricle make up the
“left portion of the heart
...
Name the chambers of the heart
...
What is pericardium? Explain its function
...
It also serves a
protective function by producing a serous fluid, which lubricates the heart and
prevents friction between the surrounding organs
...


7
...

The heart wall is made up of 3 layers, namely:

Epicardium – This is the outermost layer of the heart
...

Myocardium – This is a layer of muscle tissue that constitutes the middle layer
wall of the heart
...

Endocardium – The innermost layer that lines the inner heart chambers and
covers the heart valves
...

8
...

The blood vessels comprise:
Veins – It supplies deoxygenated blood to the heart via inferior and superior vena
cava, eventually draining into the right atrium
...

Arteries – These are muscular-walled tubes responsible for supplying oxygenated
blood away from the heart to all other parts of the body
...
What is the function of the heart valves? Provide examples of various valves
...
They prevent the backflow of blood
...

10
...
This causes oxygen deprivation in the heart
muscles, and prolonged deprivation can cause tissues to die
...
Drag and drop the correct
labels to the boxes with the matching, highlighted structures
...

 One part in the image gets highlighted
...

 After finishing all the labeling, check your answers
...
Sense Organs
To interpret the world around us, we have various senses and sense organs
...


Sense Organs Definition
“Sense organs are the organs that respond to external stimuli by conveying
impulses to the sensory nervous system
...
They
are an integral part of our lives and it is the only way that enables us to perceive
the environment
...
These senses govern our association and our interaction with the
environment
...
The
receptors could be classified into two parts viz
...

The former is present throughout the body while the latter includes
chemoreceptors, photoreceptors and mechanoreceptors
...
These senses provide an organism with information
crucial for perception
...
These are sensitive to light images
...
It helps in the sense of sight by detecting and focussing on the light images
...
Behind the lens
of the eye lies the vitreous body
...
This substance gives shape to the eyeball and also transmits light
to the very back of the eyeball, where the retina is found
...
There are two types of cells present that
perform functions distinct from each other
...

Rods: These sensors function in low light and are found at the edges of the retina
...

Cones: These types of retinal cells work best in bright light, detecting fine details
and colour
...
Typically, colour blindness occurs when any one
of these types of cones is not present
...
They help us to perceive sounds
...

This is known as hearing or audio caption
...
All sounds are basically
vibrations, so the outer ear transfers these vibrations into the ear canal, where
these vibrations are transformed by the brain into meaningful sound
...


Nose – Smell or Olfalcoception
The nose is an olfactory organ
...
This sense of organ also aids our sense of taste
...
The olfactory cells tend to line the top of the nasal cavity
...
As one breathes in, the air enters the
nasal cavity
...
These chemicals bind to the cilia, which conduct a nerve impulse that is
carried to the brain
...
During a cold, the body produces mucus which blocks the sense of smell; this
is the reason why the food which we eat tastes bland
...
It is related to the sense of touch
...
The skin contains general receptors
which can detect touch, pain, pressure and temperature
...
Skin receptors generate an impulse, and when activated, is
carried to the spinal cord and then to the brain
...
They are:

Vestibular System
The vestibular system acts as a sensory system of the body and is responsible for
transmitting information to our brain about the motions, head position and spatial
orientation
...

Maintaining our body balance
...

Identifying the orientation and posture of our bodies in relation to the
environment
...


Proprioception System
The proprioception system is described as the conscious or unconscious awareness
of joint position
...

Walking or kicking without looking at our feet, balancing on one leg, touching the
nose with eyes closed, and the ability to sense the surface on which we are
standing, are a few examples of proprioception systems
...

Deafness is defined as the condition that occurs when a person, partially or
completely loses the ability to hear
...

What is Olfaction?
Olfaction is the term mainly referred to as the sense of smell
...
There are five sense organs –
eyes, ears, nose, tongue, and skin
...

Which part of the human ear is responsible for maintaining body balance?
The inner part of the human ear called semicircular canals is responsible for
maintaining body balance
...
Cells

The cell is the most basic, structural and functional unit of life
...

Cells are the basic, fundamental unit of life
...


“A cell is defined as the smallest, basic unit of life that is responsible for all of life’s
processes
...
A cell can
replicate itself independently
...

Each cell contains a fluid called the cytoplasm, which is enclosed by a membrane
...
Moreover, cellular structures called cell organelles are suspended in the
cytoplasm
...
The study of cells from their
basic structure to the functions of every cell organelle is called Cell Biology
...


Discovery of Cells

Discovery of cells is one of the remarkable advancements in the field of science
...
The structure and functions of cells helped us
to understand life in a better way
...
Robert Hooke observed a piece of bottle
cork under a compound microscope and noticed minuscule structures that
reminded him of small rooms
...

However, his compound microscope had limited magnification, and hence, he
could not see any details in the structure
...

Later Anton Van Leeuwenhoek observed cells under another compound
microscope with higher magnification
...
As a result, Leeuwenhoek concluded
that these microscopic entities were “alive
...

In 1883, Robert Brown, a Scottish botanist, provided the very first insights into the
cell structure
...

All organisms are made up of cells
...
Mycoplasmas are the smallest known
cells
...
They provide structure to the
body and convert the nutrients taken from the food into energy
...

They are of different shapes and sizes, pretty much like the bricks of the buildings
...

Cells are at the lowest level of organization in every life form
...
Humans have more number of cells
compared to that of bacteria
...

 The cell interior is organized into different individual organelles surrounded
by a separate membrane
...

 Every cell has one nucleus and membrane-bound organelles in the
cytoplasm
...

 Lysosomes digest unwanted materials in the cell
...

 Cells comprise several cell organelles that perform specialized functions to
carry out life processes
...
The
hereditary material of the organisms is also present in the cells
...
Various types of cells perform different
functions
...
Instead, some prokaryotes such as
bacteria have a region within the cell where the genetic material is freely
suspended
...

 They all are single-celled microorganisms
...


 The cell size ranges from 0
...
5 µm in diameter
...

 Prokaryotes generally reproduce by binary fission, a form of asexual
reproduction
...


Eukaryotic Cells





Eukaryotic cells are characterized by a true nucleus
...

This broad category involves plants, fungi, protozoans, and animals
...
It is also responsible
for cell to cell communication
...

 There are some contrasting features between plant and animal cells
...
, the plant cell contains chloroplast, central vacuoles, and other
plastids, whereas the animal cells do not
...
These components include- cell wall, cell
membrane, cytoplasm, nucleus, and cell organelles
...


Cell Membrane
 The cell membrane supports and protects the cell
...
It separates the cell from
the external environment
...

 The cell membrane is the outer covering of a cell within which all other
organelles, such as the cytoplasm and nucleus, are enclosed
...


 By structure, it is a porous membrane (with pores) that permits the
movement of selective substances in and out of the cell
...

 It forms the wall-like structure between two cells as well as between the
cell and its surroundings
...
The cell wall helps to reinforce this function
...
It is
made up of cellulose, hemicellulose, and pectin
...
It protects the plasma
membrane and other cellular components
...

 It is a rigid and stiff structure surrounding the cell membrane
...


Cytoplasm
 The cytoplasm is a thick, clear, jelly-like substance present inside the cell
membrane
...

 The cell organelles such as endoplasmic reticulum, vacuoles, mitochondria,
and ribosomes, are suspended in this cytoplasm
...

 It sends signals to the cells to grow, mature, divide and die
...

 The nucleus protects the DNA and is an integral component of a plant’s cell
structure
...
The cell theory states that:
 All living species on Earth are composed of cells
...

 All cells arise from pre-existing cells
...
Important functions of the cell are as follows:

Provides Support and Structure
All organisms are made up of cells
...

The cell wall and the cell membrane are the main components that function to
provide support and structure to the organism
...
, the skin is made up of a
large number of cells
...


Facilitate Growth Mitosis
In the process of mitosis, the parent cell divides into the daughter cells
...


Allows Transport of Substances
Various nutrients are imported by the cells to carry out various chemical processes
going on inside the cells
...
Small molecules such as
oxygen, carbon dioxide, and ethanol diffuse across the cell membrane along the
concentration gradient
...
The larger molecules
diffuse across the cell membrane through active transport where the cells require
a lot of energy to transport the substances
...
This energy is
produced by the cells through a process called photosynthesis in plants and
respiration in animals
...
Mitosis
is termed as asexual reproduction where the parent cell divides to form daughter
cells
...

Thus, we can understand why cells are known as the structural and functional unit
of life
...


Frequently Asked Questions
1
...


2
...

 Cells provide the necessary structural support to an organism
...

 Structurally, the cell has cell organelles which are suspended in the
cytoplasm
...

 Lysosomes digest metabolic wastes and foreign particles in the cell
...


3
...

The cell structure comprises several individual components which perform
specific functions essential to carry out life processes
...
State the types of cells
...
Elaborate Cell Theory
...
The cell theory states that:
 All living species on Earth are composed of cells
...

 All cells arise from pre-existing cells
...
What is the function of mitochondria in the cells?
Mitochondria are known as the powerhouse of the cells
...
It also regulates cellular
metabolism
...
What are the functions of the cell?

The essential functions of the cell include:





The cell provides support and structure to the body
...

It helps in reproduction
...


8
...
It creates lysosomes and
transports lipids around the cells
...
Who discovered the cell and how?
Robert Hooke discovered cells in 1665
...

Consequently, he named his discovery “cells
...
Name the cell organelle that contains hydrolytic enzymes capable
of breaking down organic matter
...
Which cellular structure regulates the entry and exit of molecules
to and from the cell?
Cell membrane
...




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