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Objects having characteristics of cellular organization, Growth, Reproduction, ability to sense Environment and give response are living organisms.
There are some important features of living organisms:
- It should grow, which means its structure changes as time goes by in an advantageous manner.
- It should show adaptation to the environment.
- It should maintain some balanced conditions in its inner structure. This is called Homeostasis.
- Its structure is highly organized.
- It should be able to break down or build up nutrients to release or store energy based on need. This is called Metabolism.
- It should be able to reproduce itself.
Classification of living world
The practice of classifying organisms is called taxonomy. Linneaeus developed a hierarchy of groups for taxonomy. To distinguish different levels of similarity, each classifying group, called taxon (pl. taxa) is subdivided into other groups. To remember the order, it is helpful to use a mnemonic device. The taxa in hierarchical order:
Domain – Archea, Eubacteria, Eukaryote
Archea (Archeabacteria) consists of archeabacteria, bacteria which live in extreme environments. The kingdom Archaea belongs to this domain.
Eubacteria consists of more typical bacteria found in everyday life. The kingdom Eubacteria belongs to this domain.
Eukaryote encompasses most of the world’s visible living things. The kingdoms Protists, Fungi, Plantae, and Animalia fall under this category.
Kingdom – Plantae, Animalia, Fungi, Protists, Eubacteria (Monera), Archaebacteria
Phylum
Class
Order
Family
Genus
Species : smallest classification
Cell structure and its functions
Cell is the smallest structural and functional unit of an organism, which is typically microscopic and consists of cytoplasm and a nucleus enclosed in a membrane.
Structure of cell
The cell is a basic unit for life forms. As well as enabling sophisticated control of biochemical processes by providing compartments and regulating chemical fluxes between them, cells also have structural Integrity and can exert forces. In the case of multicellular organisms (animals and Plants), each cell contributes some mechanical property to the tissue it forms together with other cells. Furthermore, many cells are eliminated during the life of a complex organism (e.g. skin layers in animals), which entails cell division and restructuring of the organisation with neighbours. Some types of cell are actually very motile, moving through Tissues (e.g. various immune system cells and some cancer cells). This dynamic aspect is even more obvious during the development of multicellular organisms, when many stages of cell division and Migration take place.
A first division of organisms is between those whose cells have within them a nucleus, the structure containing most of the genetic material in the form of DNA, and those whose cells don’t. The nucleated cells are called eukaryotic and are found in animals, plants, fungi, protozoa and algae. In contrast, bacteria (and the less common archaea) do not have a nucleus and their DNA is spread throughout the cell. These cells are called prokaryotic. Eukaryotic organisms can be unicellular or multicellular while all prokaryotes are unicellular.
Some of the important cell oragenells are as follows:
The Nucleus
A cell nucleus is the part of the cell which contains the genetic code, the DNA. The nucleus is small and round, and it works as the cell’s control center. It contains Chromosomes which house the DNA. The human body contains billions of cells, most of which have a nucleus. All eukaryote organisms have nuclei in their cells, even the many eukaryotes that are single-celled. Bacteria and Archaea, which are prokaryotes, are single-celled organisms of quite a different type and do not have nuclei. Cell nuclei were first found by Antonie van Leeuwenhoek in the 17th century.
The nucleus has a membrane around it but the things inside it do not. Inside it are many proteins, RNA Molecules, chromosomes and the nucleolus. In the nucleolus ribosomes are put together. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA into proteins. When a cell is dividing or preparing to divide, the chromosomes become visible with a Light Microscope. At other times when the chromosomes are not visible, the nucleolus will be visible.
Endoplasmic reticulum
The endoplasmic reticulum is a collection of interconnected tubes and flattened sacs that begin at the nucleus and ramble through the cytoplasm. There are two types of endoplasmic reticulum distinguished by the presence or absence of ribosomes.
Rough ER consists of stacked, flattened sacs with many ribosomes attached; oligosaccharide groups are attached to polypeptides as they pass through on their way to other organelles or to secretory vesicles.
Smooth ER has no ribosomes; it is the area from which vesicles carrying proteins and lipids are budded; it also inactivates harmful chemicals.
Golgi bodies
The Golgi apparatus or Golgi complex is found in most cells. It is another packaging organelle like the endoplasmic reticulum (ER). It was named after Camillo Golgi, an Italian biologist. It is pronounced GOL-JI in the same way you would say squee-gie, as soft a “G” Sound. While layers of membranes may look like the rough ER, they have a very different function.
The Golgi apparatus gathers simple molecules and combines them to make molecules that are more complex. It then takes those big molecules, packages them in vesicles, and either stores them for later use or sends them out of the cell. It is also the organelle that builds lysosomes (cell digestion machines). Golgi complexes in the plant may also create complex sugars and send them off in secretory vesicles. The vesicles are created in the same way the ER does it. The vesicles are pinched off the membranes and float through the cell.
Mitochondria
Mitochondria are rod-shaped organelles that can be considered the power generators of the cell, converting Oxygen and nutrients into adenosine triphosphate (ATP). ATP is the chemical energy “currency” of the cell that powers the cell’s metabolic activities. This process is called aerobic Respiration and is the reason animals breathe oxygen. Without mitochondria (singular, mitochondrion), higher animals would likely not exist because their cells would only be able to obtain energy from anaerobic respiration (in the absence of oxygen), a process much less efficient than aerobic respiration. In fact, mitochondria enable cells to produce 15 times more ATP than they could otherwise, and complex animals, like humans, need large amounts of energy in order to survive.
The number of mitochondria present in a cell depends upon the metabolic requirements of that cell, and may range from a single large mitochondrion to thousands of the organelles. Mitochondria, which are found in nearly all eukaryotes, including plants, animals, fungi, and protists, are large enough to be observed with a light microscope and were first discovered in the 1800s. The name of the organelles was coined to reflect the way they looked to the first scientists to observe them, stemming from the Greek words for “thread” and “granule.” For many years after their discovery, mitochondria were commonly believed to transmit hereditary information. It was not until the mid-1950s when a method for isolating the organelles intact was developed that the modern understanding of mitochondrial function was worked out.
Vesicles: There are two types of vesicles: lysosomes and Peroxisomes
Lysosomes: Lysosomes are membrane-enclosed organelles that contain an array of ENZYMES capable of breaking down all types of biological polymers—proteins, nucleic acids, Carbohydrates, and lipids. Lysosomes function as the Digestive System of the cell, serving both to degrade material taken up from outside the cell and to digest obsolete components of the cell itself. In their simplest form, lysosomes are visualized as dense spherical vacuoles, but they can display considerable variation in size and shape as a result of differences in the materials that have been taken up for digestion . Lysosomes thus represent morphologically diverse organelles defined by the common function of degrading intracellular material.
Peroxisomes
Peroxisomes are small, membrane-enclosed organelles that contain enzymes involved in a variety of metabolic reactions, including several aspects of energy metabolism. Although peroxisomes are morphologically similar to lysosomes, they are assembled, like mitochondria and chloroplasts, from proteins that are synthesized on free ribosomes and then imported into peroxisomes as completed polypeptide chains. Although peroxisomes do not contain their own genomes, they are similar to mitochondria and chloroplasts in that they replicate by division.
Some specialized Plant Organelles
Plastids: There are three types of plastids: Chloroplasts, Chromoplasts, Amyloplasts
Chloroplasts are oval or disk shaped, bounded by a double membrane, and critical to the process of Photosynthesis.Chromoplasts have carotenoids, which impart red-to-yellow colors to plant parts, but no chlorophyll. Amyloplasts have no pigments; they store starch grains in plant parts such as potato tubers.
Central Vacuole
Vacuoles are essentially membrane-bound sacs found in the cytoplasm. In animal cells, vacuoles are relatively small, and are used as temporary storage areas for materials and for transport purposes. In plant cells, however, there is generally a large single central vacuole. Comprising approximately 90% of an mature plant cell, the central vacuole provides structure and support to the cell by maintaining turgor pressure, which is essentially fluid pressure that keeps the cells rigid. They are necessary to cell functions in many different ways such as maintaining cell structure and storing nutrients, waste products, and many other substances. Below is a picture of a central vacuole in a cell.
Functions of cell
Structure and support: Like a classroom is made of bricks, every organism is made of cells. While some cells such as the collenchyma and sclerenchyma are specifically meant for structural support, all cells generally provide the structural basis of all organisms. For instance, skin is made up of a number of skin cells. Vascular plants have evolved a special tissue called xylem, which is made of cells that provide structural support.
Growth: In complex organisms, tissues grow by simple multiplication of cells. This takes place through the process of mitosis in which the parent cell breaks down to form two daughter cells identical to it. Mitosis is also the process through which simpler organisms reproduce and give rise to new organisms.
Transport: Cells import nutrients to use in the various chemical processes that go on inside them. These processes produce waste a cell needs to get rid of. Small molecules such as oxygen, carbon dioxide and ethanol get across the cell membrane through the process of simple diffusion, which is regulated with a concentration gradient across the cell membrane. This is known as passive transport. However, larger molecules, such as proteins and polysaccharides, go in and out of a cell through the process of active transport in which the cell uses vesicles to excrete or absorb larger molecules.
Energy production: An organism’s survival depends upon the thousands of chemical reactions that cells carry out relentlessly. For these reactions, cells require energy. Most plants get this energy through the process of photosynthesis whereas respiration is the mechanism that provides energy to animal cells.
Metabolism: Metabolism includes all the chemical reactions that take place inside an organism to keep it alive. These reactions can be catabolic or anabolic. The process of energy production by breaking down molecules (glucose) is known as catabolism. Anabolic reactions, on the other hand, use energy to make bigger substances from simpler ones.
Reproduction: Reproduction is vital for the survival of a species. A cell helps in reproduction through the processes of mitosis (in more evolved organisms) and meiosis. In mitosis cells simply divide to form new cells. This is termed as asexual reproduction. Meiosis takes place in gametes or reproductive cells in which there is a mixing of genetic information. This causes daughter cells to be genetically different from the parent cells. Meiosis is a part of sexual reproduction.,
Plants are essential to life on Earth. They provide us with food, medicine, fuel, fiber, and other products that we use every day. They also play a vital role in the environment, helping to regulate the Climate and provide habitat for other organisms.
Plants are the foundation of agriculture. They provide us with the food that we eat, including grains, fruits, vegetables, and nuts. Agriculture is a major Industry that employs millions of people around the world.
Food
Plants are a major source of food for humans and animals. They provide us with carbohydrates, protein, VITAMINS, and Minerals. Some of the most important Food Crops include wheat, rice, corn, soybeans, and potatoes.
Medicine
Plants have been used for medicinal purposes for centuries. Many modern medicines are derived from plants, including aspirin, quinine, and morphine. Plants are also used to make herbal remedies for a variety of Health conditions.
Fuel
Plants can be used to produce biofuels, such as ethanol and biodiesel. Biofuels are renewable sources of energy that can help to reduce our reliance on fossil fuels.
Fiber
Plants are a source of fiber, which is important for digestive health. Fiber is also used to make paper, textiles, and other products.
Ornament
Plants are used for ornamental purposes in gardens, parks, and homes. They can be used to create beautiful landscapes and add color and life to our surroundings.
Recreation
Plants are used for recreation in a variety of ways. People enjoy gardening, hiking, and camping in natural areas. Plants are also used in Sports, such as golf and baseball.
Characteristics of Plants
Plants are autotrophic, meaning that they can make their own food. They do this through photosynthesis, a process that uses sunlight to convert carbon dioxide and water into glucose and oxygen.
Plants are multicellular, meaning that they are made up of many cells. Plant cells have a cell wall that is made of cellulose. Cellulose is a strong, fibrous material that gives plants their structure.
Plants have chloroplasts, which are organelles that contain chlorophyll. Chlorophyll is a green pigment that absorbs sunlight and uses it in photosynthesis.
Plants are sessile, meaning that they cannot move from place to place. They are anchored to the ground by their roots.
Plants have vascular tissue, which is a system of tubes that transports water and nutrients throughout the plant.
Plants have seeds, which are reproductive structures that contain the embryo of a new plant.
Structure and Function of Plant Cells and Organelles
The cell membrane is a thin layer that surrounds the cell. It controls what enters and leaves the cell.
The cell wall is a rigid structure that provides support for the cell. It is made of cellulose, a strong, fibrous material.
The cytoplasm is the jelly-like substance inside the cell. It contains organelles, which are specialized structures that carry out different functions in the cell.
The nucleus is the control center of the cell. It contains the cell’s DNA, which is the blueprint for the cell’s structure and function.
The chloroplast is an organelle that contains chlorophyll. Chlorophyll is a green pigment that absorbs sunlight and uses it in photosynthesis.
The mitochondrion is an organelle that produces energy for the cell.
The ribosome is an organelle that makes proteins.
The vacuole is a large, fluid-filled organelle that stores nutrients and waste products.
The Golgi apparatus is an organelle that packages and distributes proteins and other molecules.
The lysosome is an organelle that breaks down waste products and damaged cells.
The peroxisome is an organelle that breaks down fatty acids and other molecules.
Conclusion
Plants are essential to life on Earth. They provide us with food, medicine, fuel, fiber, and other products that we use every day. They also play a vital role in the environment, helping to regulate the climate and provide habitat for other organisms.
Plants and mankind
- What are the benefits of plants?
Plants provide us with food, oxygen, and shelter. They also help to regulate the climate and clean the air.
- What are the challenges facing plants?
Plants are facing a number of challenges, including Climate Change, deforestation, and pollution. These challenges are threatening the survival of many plant species.
- What can we do to help plants?
We can help plants by reducing our carbon footprint, planting trees, and supporting Sustainable Agriculture.
Characteristics of plants
- What are the characteristics of plants?
Plants are multicellular organisms that are photosynthetic. They have a cell wall made of cellulose, and they reproduce sexually.
- How do plants grow?
Plants grow by taking in nutrients from the Soil and sunlight. They use these nutrients to produce new cells, which allow them to grow taller and larger.
- What are the different types of plants?
There are many different types of plants, including trees, shrubs, herbs, and Grasses. Each type of plant has its own unique characteristics.
Structure and function of plant cells and organelles
- What are the different parts of a plant cell?
The different parts of a plant cell include the cell wall, the cell membrane, the cytoplasm, the nucleus, the mitochondria, the chloroplasts, and the vacuole.
- What are the functions of the different parts of a plant cell?
The cell wall provides support and protection for the cell. The cell membrane controls what enters and leaves the cell. The cytoplasm is the jelly-like substance that fills the cell. The nucleus is the control center of the cell. The mitochondria produce energy for the cell. The chloroplasts capture sunlight and use it to produce food for the cell. The vacuole stores water and other nutrients.
- How do plant cells work together?
Plant cells work together to form tissues, which in turn form organs. The different tissues and organs of a plant work together to carry out the functions necessary for the plant to survive.
Question 1
Which of the following is not a characteristic of plants?
(A) They are multicellular organisms.
(B) They are photosynthetic.
(C) They are heterotrophic.
(D) They have a cell wall.
Answer
(C)
Plants are autotrophic, meaning they can produce their own food through photosynthesis. Heterotrophic organisms cannot produce their own food and must consume other organisms to survive.
Question 2
Which of the following is not a part of a plant cell?
(A) Chloroplast
(B) Cell wall
(C) Nucleus
(D) Mitochondria
Answer
(D)
Mitochondria are found in animal cells, not plant cells.
Question 3
Which of the following is not a function of the chloroplast?
(A) Photosynthesis
(B) Cellular respiration
(C) Storage of food
(D) Synthesis of proteins
Answer
(B)
Cellular respiration is a process that occurs in all cells, not just plant cells. It is the process by which cells break down glucose to produce energy.
Question 4
Which of the following is not a function of the nucleus?
(A) Control of cell activities
(B) Storage of genetic information
(C) Synthesis of proteins
(D) Production of energy
Answer
(D)
The nucleus is the control center of the cell. It contains the cell’s DNA, which is the blueprint for the cell’s structure and function. The nucleus also controls the synthesis of proteins and other molecules that are essential for the cell’s survival.
Question 5
Which of the following is not a function of the cell wall?
(A) Protection of the cell
(B) Support of the cell
(C) Transport of materials into and out of the cell
(D) Synthesis of proteins
Answer
(D)
The cell wall is a rigid structure that surrounds the cell membrane. It provides protection and support for the cell. The cell wall also helps to regulate the transport of materials into and out of the cell.
Question 6
Which of the following is not a type of plant tissue?
(A) Epidermal tissue
(B) Ground tissue
(C) Vascular tissue
(D) Muscle tissue
Answer
(D)
Muscle tissue is found in animals, not plants. Plant tissues are classified into three types: epidermal tissue, ground tissue, and vascular tissue.
Question 7
Which of the following is not a function of epidermal tissue?
(A) Protection of the plant
(B) Absorption of water and minerals
(C) Transport of water and minerals
(D) Photosynthesis
Answer
(D)
Photosynthesis is a process that occurs in chloroplasts, which are found in plant cells. Epidermal tissue does not contain chloroplasts and therefore does not participate in photosynthesis.
Question 8
Which of the following is not a function of ground tissue?
(A) Storage of food
(B) Production of new cells
(C) Transport of water and minerals
(D) Photosynthesis
Answer
(D)
Photosynthesis is a process that occurs in chloroplasts, which are found in plant cells. Ground tissue does not contain chloroplasts and therefore does not participate in photosynthesis.
Question 9
Which of the following is not a function of vascular tissue?
(A) Transport of water and minerals
(B) Transport of food
(C) Support of the plant
(D) Photosynthesis
Answer
(D)
Photosynthesis is a process that occurs in chloroplasts, which are found in plant cells. Vascular tissue does not contain chloroplasts and therefore does not participate in photosynthesis.
Question 10
Which of the following is not a type of plant organ?
(A) Root
(B) Stem
(C) Leaf
(D) Muscle
Answer
(D)
Muscle tissue is found in animals, not plants. Plant organs are classified into three types: roots, stems, and leaves.