BIOLOGY FORM ONE TOPIC 3: CELL STRUCTURE AND ORGANIZATION, TOPIC 4: CLASSIFICATION OF LIVING THINGS
The Concept of Cell
The Meaning of the Cell
Explain the meaning of the cell
Plants
and animals are made up of units called cells. The cells are
microscopic in such a way that they cannot be seen by our naked eyes.
Some organisms like protozoa, diatoms and bacteria consist of one cell
and are called single-celled or unicellular organisms. Some are made up
of many cells and are called multicellular organisms.
The
cell structure of living things was first seen by Robert Hooke in 1667
when he examined fine slices of cork. Robert Hooke believed that the
cells were empty and that the cell wall and cell membrane were the most
important parts of the cell but now cell contents are seen to be the
most important ones. Therefore a cell can be defined as the smallest unit of living things or a cell is a basic unit of life.
The Characteristics of the Cell
Mention the characteristics of the cell
Characteristics of the cell include the following:
- Cells are small microscopic structures which cannot be seen by our naked eyes.
- Cells are capable of dividing by mitotic process or meiotic process.
- Cells contain structures called organelles.
The cell theory
- A cell is a basic unit of structure and function in living organisms.
- New cells only come from pre-existing ones.
- Cells contain structures called organelles.
The
cell theories were proposed jointly by two scientists namely Schleiden,
a Belgian botanist, in 1838 and Schwann, German Zoologist, in 1839
Difference Between Various Types of Cells
Differentiate various types of cells
PROKARYOTIC AND EUKARYOTIC CELLS
Prokaryotic cells
are cells with no membrane-bound nucleus. The DNA lies free in the
cytoplasm in a region known as nucleoid. They have no true nuclei.
Examples of prokaryotic organisms are bacteria.
Eukaryotic cells are
cells whose nuclei are bounded by nuclear membrane. They are surrounded
by two nuclear membranes called nuclear envelope. Examples of
eukaryotic organisms are protoctists, fungi, plants and animal cells.
Differences between cell wall and cell membrane
| Cell wall | Cell membrane |
| It is a non–living structure | It is a living structure |
| It is made up of cellulose | It is made up of lipoprotein |
| It is freely permeable | It is selectively permeable |
Different between prokaryotic and Eukaryotic cells
| Eukaryotic cells | Prokaryotic cell |
| They have nuclear membrane | Lack nuclear membrane |
| Organelles are surrounded by envelopes | Organelles are not surrounded by envelopes |
| Have true nucleus | Have no true nucleus |
The Functions of Different Parts of Plant and Animal Cells
Explain the functions of different parts of plant and animal cells
Basically a cell has three main parts
- Cell membrane
- Cytoplasm
- Nucleus
Cell membrane (plasmalemma)
This is a thin flexible membrane made of protein and oil. It has the following functions:
- The cell membrane encloses the contents of the cell.
- It is freely permeable to water and gases only and selectively permeable to other molecules e.g. it allows food in but keeps unwanted molecules out. Thus cell the membrane controls the substances entering and leaving the cell.
Cytoplasm
Cytoplasm
is a transparent jelly-like fluid and may contain particles such
chloroplasts or starch grains or oil droplets. It contains up to 80%
water and the remainder is mainly protein. It is a place where chemical
reactions take place
Nucleus
A
nucleus is a ball-shaped or oval body located inside the cytoplasm. It
cannot usually be seen unless the cell has been stained with certain
dyes. It consists of nucleoplasm bounded by nuclear membrane. The
nucleus is a cell control centre.
The following are the functions of the nucleus:
- It controls the formation and development of a cell.
- The nucleus also controls chemicals which the cell manufactures.
- The nucleus contain chromosomes which carry genetic material i.e. DNA which is responsible for controlling genetic information.
Cell wall
The
cell wall is only found in plant cells. It is made up of cellulose.
When the cell is growing the cell wall is fairy plastic and extensible.
It becomes tough and resists stretching when the cell has reached full
size. The cell wall is non-living. It has the following functions:
- It gives the cell its shape.
- It is freely permeable to all kinds of molecules.
- It supports and protects the cell.
- It supports non-woody plant organs, such as leaves, by turgor pressure.
- It osmoregulates by resisting entry of excess water into cell.
Vacuole
In
animal cells, vacuoles are small droplets of fluid in the cytoplasm
variable in size and position. In plant cells, the vacuole is a large,
permanent fluid-filled cavity which occupies a greater part of the cell.
In plants, the fluid is called cell sap. The cell sap may contain salts, sugar and pigments dissolved in water.
The vacuole performs the following functions:
- It is responsible for food storage and osmoregulation.
- The outward pressure of the vacuole on the cell wall makes the plant cells firm, giving strength and resilience to the tissues.
Mitochondria
Mitochondria
are found in all aerobic eukaryotic cells. A mitochondrion is
surrounded by an envelope of two membranes, the inner being folded to
form cristae (singular: crista) It contains a matrix with a few ribosomes, a circular DNA molecule and phosphate granules.
Mitochondrion
A
mitochondrion is a power house of a cell. It contains respiratory
enzymes involved in respiration. It absorbs oxygen and glucose. The
glucose is broken down to CO2 and H2O. Energy is released from glucose bonds to form ATPs (for use in other vital functions e.g. growth, movement, etc.
Chloroplast
Chloroplasts
are disc-shaped organelles. They are found in plant cells and algae
cells. A chloroplast contains a green substance called chlorophyll. It
is surrounded by an envelope of two membranes and contains gel-like
stroma through which runs a system of membranes that are stacked in
places to form grana.
Chloroplast
Chloroplast
is an organelle in which photosynthesis takes place, producing sugars
from carbon dioxide and water using light energy trapped by chlorophyll.
Golgi body
Golgi bodies are stacks of flattened, membrane-bound sacs
Golgi bodies have the following functions:
- Golgi bodies are responsible for internal processing and transport system.
- Processing of many cell materials e.g. protein takes place in the cisternae.
- Godgi vesicles transport the materials to the other parts of the cell
Plant and Animal Cell
Draw and label plant and animal cell
Animal cell
Plant cell
Similarities and Differences of Plant and Animal Cells
Outline similarities and differences of plant and animal cells
Differences between plant cell and animal cells
| PLANT CELL | ANIMAL CELL |
| (i) Have definite shape | Have no definite shape |
| (ii) Have chloroplasts | Have no chloroplasts |
| (iii)Have large permanent vacuoles | Have small temporary vacuoles |
| (iv) Centrioles usually absent | Centrioles present |
| (v) Have cell wall made of cellulose | Have no cell wall |
| (vi) The nucleus is located at the periphery | The nucleus is centrally located |
Similarities between animal cell and plant cells
- Both have cell membranes
- Both contain cytoplasm
- Both have nucleus
- Both have mitochondria
- Both have golgi bodies
- Both have ribosomes
Cell Differentiation
The Concept of Cell Differentiation
Explain the concept of cell differentiation
When most cells have finished dividing they become specialized. This means that:
- They do one particular job
- They develop a distinct shape
- Special kinds of chemical change take place in their cytoplasm
The
changes in shape and chemical reactions enable the cell to carry out
its special function. The process by which cells are specialized to
perform a particular function is called cell differentiation or ‘division of labour’
within the organism. Similarly, the special functions of mitochondria,
ribosomes and other cell organelles may be termed as division of labour
within the cell.
The Importance of Cell Differentiation and Formation of Tissues, Organs and Body Systems
Outline the importance of cell differentiation and formation of tissues, organs and body systems
Humans have many different types ofcellswith different jobs, such as bloodcellsthat carry oxygen and nervecellsthat transmit signals to all parts of the body.Cell differentiationis the process by whichcellsbecome specialized in order to perform different functions.
Even
multicellular organisms begin as just a single cell. Getting from one
single cell to billions of specialized cells that perform different
functions is a process that happens with the regulation of DNA and RNA.
It can also be influenced by factors in the environment.
Cell
differentiation holds a lot of importance for two basic reasons.
Firstly, it helps to identify stem cells, which could be used in the
future to deal with conditions that require transplant and form the
basis of embryonic stem cell research. Also, in cytopathology, the level
of cellular differentiation is used as a measure of cancer progression,
where the term 'grade' is used as a marker to determine how
differentiated a cell in a tumor is. Thus, the importance of this
process cannot be underestimated as it could hold the key to future
treatments for fatal diseases.
Difference between Cells, Tissues Organs and Body Systems
Differentiate cells, tissues organs and body systems
Animal cells
Nerve cells
These
are specialized for conducting impulses of an electrical nature along
the fibre. The fibre may be very long e.g. from the foot to the spinal
column. They are the longest cells known.
Nerve cell
Blood cells
- White blood cells:These cells occur in blood stream and are specialized for engulfing harmful bacteria. They are able to change their shapes and move about, even through the walls of blood vessels into the surrounding tissue.
White blood cell
- Red blood cells:These cells are responsible for transportation of oxygen from the lungs to all parts of the body.
Red blood cells
- Platelet cells: Platelet cells are found in the blood. They are also called blood platelets. Their function is to help clot the blood at wounds and so stop bleeding.
Reproductive cells
- Sperm cell: it is a male gamete produced in the testes.
Sperm cell
- Egg cell:It is a female gamete produced in the ovary.
Egg cell
Muscle cells
These
are elongated cells which form the muscle tissues. Muscle cells are
highly specialized in that they are able to shorten a half or even a
third of their resting lengths. This characteristic enables the muscles
to contract and expand.
Muscle cell
Ciliated cells
These cells form the lining of the nose and wind pipe.
Plant cells
Root hair cells
These
cells form the outer layer of young roots. The cells are specialized to
absorb water and mineral slats from the soil. The hair-like projections
penetrate the soil particles and offer a large absorbing surface.
Phloem cells
These
are food conducting cells in a plant, joined end to end, and where they
meet, perforations occur in the walls. Through these holes, the
cytoplasm of one cell communicates with the next.
Xylem cells
The
cells conduct water and mineral salts form the soil to all parts of the
plant. They are also responsible for mechanical support.
- Parenchyma cells
- Collenchyma cells
- Sclerenchyma cells
- Epidermal cells
TISSUES
A tissue is a group or collection of similar cells performing a specific function. Tissues vary in size, shape and function.
Examples of tissues
Animal tissues
Animal tissues include epithelial tissue, muscle tissue, nervous tissue, blood tissue and bony tissue.
Epithelial tissue:Epithelial
tissues cover the body lining cavities, hollow organs and tubes. They
are responsible for(i) protection of the underlying structure from
dehydration, and chemical and mechanical damages;(ii) secretion;
and(iii) absorption.
Columnar epithelium
Squamous epithelium
Cuboidal epithelium
Stratified epithelium
Cliated columnar
Cilliated columnar epithelium with goblet cells
Muscle tissue
Muscle tissue consists of cells specialized to contract and move the body. Muscle tissues can be:
- skeletal muscle tissue;
- smooth muscle tissue; or
- cardiac muscle tissue.
Skeletal muscle tissues form those muscles that move the bones
Skeletal muscle fibres
Smooth muscle tissues
These are found in the walls of hollow organs. They perform the following functions:
- Regulate the diameter of blood vessels and parts of the respiratory tract.
- Propel the contents of the ureters, ducts of glands and alimentary tract.
- Expel contents of the urinary bladder and uterus.
Smooth muscle fibres
Cardiac muscle tissue
This
kind of muscle tissue is found only in the heart wall. It helps in
contracting and relaxing of heart muscles thus pumping the blood to
various body parts.
Cardiac muscle fibres
Nervous tissues
Nervous
tissues have endings that detect changes in the environment. They
transmit and conduct nerve impulses to the brain and spinal cord and to
the effector organs.
Plant tissues
Examples
of plant tissues are collenchyma tissue, sclerenchyma tissue, epidermal
tissue, conducting tissues e.g. phloem and xylem, palisade tissue and
spongy tissue.
An onion epidermal tissue
ORGANS
An organ is a collection of tissues working together to perform a certain function
Animal organs
Other examples of animal organs include skin, testes, ears, noses and the brain.
Plant organs
Examples of plant organs include leaves, stems, roots, flowers and fruits.
Plant organs
Organ system
A system refers to several inter-related organs performing a particular function.
Digestive system
The
main organs that make up the digestive system are alimentary canal,
liver and pancreas.The main function of this system is to digest and
absorb food.
The digestive system
Circulatory system
This
system consists of the heart, arteries and veins.The role of the
circulatory system is to transport gases, food, hormones and distribute
heat.
The circulatory system
Lymphatic system
Lymphatic
system has comprises of the lymph vessels and lymph nodes. The main
function of the lymphatic system is to transport materials and protect
against.
Lymphatic system
Respiratory system
The
respiratory system consists of the trachea and the lungs. The role of
the respiratory system is to take in oxygen and expel carbon dioxide
gas.
The respiratory system
The urinary system
The
main organs of the urinary system are kidneys, ureter, bladder and
urethra.The urinary system plays a role in removing metabolic waste
products from the body and also it is responsible for osmoregulation.
The urinary system
The nervous system
This system consists of the brain, spinal cord and nerves.The role of the nervous system is to detect and respond to stimuli.
Muscular system
The muscular system
It consists of the organs muscles and tendons. The role of the muscular system is to bring about movement.
The skeletal muscles
The reproductive system
It consists of the ovaries, testes and uterus. Its role is to produce offspring.
Male reproductive system
Female reproductive system
Endocrine system
It consists of endocrine glands. Its role is to produce hormones.
Endocrine system
Skeletal system
It consists of a system of skeletons. Its function is to support the body, protect internal organs and produce blood cells.
Skeletal system
Examples of organ system in plants
Root system –consists of roots
Function:
- Holds the plant firmly into the soil
- Absorption of water and mineral salts from the soil
- Sometimes they act as storage organs in some plants
Shoot system – consists of the organs flowers, fruits, stem and leaves
Function
- Site of reproduction
- Transport of substances
- Photosynthesis occurs in the shoot
- Transpiration processes.
TOPIC 4: CLASSIFICATION OF LIVING THINGS
Concept of Classification
Viruses
Viruses
were discovered by a Russian botanist D. I. Ivanovsky and a Dutchman
Beijerink.In 1852 Ivanovsky prepared an infectious extract from tobacco
plants that were suffering from mosaic disease. When the extract was
passed through a filter able to prevent the passage of bacteria, the
filtered fluid was still infectious. 1898 Beijerink gave the name
“virus” (in latin means, “poison”) to describe the infectious nature of
certain filtered plant fluids.
General and Distinctive Features of Viruses
Explain general and distinctive features of viruses
Characteristics of Viruses
- They are the smallest living organisms ranging from 20-30nm. On average, they are about 50times smaller than bacteria.
- Viruses do not have cellular structures, which mean that they lack certain important organelles like nucleus, cytoplasm, golgi bodies, etc.
- They can only reproduce inside the living cells hence they are parasitic.
- They have a simple structure consisting of either DNA or RNA but not both, surrounded by a protein or lipoprotein coat.
- They can be described as living or non-living.
- They are highly specific to their hosts i.e. each virus recognizes only certain types of cells.
- Viruses are capable of replicating themselves only when they are inside the host cell.
Viruses as living things
- They possess genetic material (RNA or DNA).
- They reproduce when they are in the host cell (replication).
- They are capable of identifying their hosts and attack them.
- They can undergo mutation (they mutate) i.e. they undergo different changes in shape.
- Like other parasites, they are specific to host.
Viruses as non-living things
- They can crystallize outside the host.
- They are metabolically inert in isolation.
- They are non-cellular i.e. they lack cell organelles.
- They do not perform necessary life processes such as respiration, excretion nutrition etc.
The Structure of Viruses
Describe the structure of viruses
Generally viruses have a very simple structure consisting of the following:
- RNA or DNA which may be single stranded or double stranded. They form a structure called core.
- A protective coat of protein surrounding the core called capsid.
- A nucleocapsid which is a combined structure of core and capsid.
- Envelope – an additional layer of lipoprotein layer around the capsid.
- Capsids are made up of identical repeating units known as capsomeres.
Bacteriophage
Bacteriophage is a virus that attacks and kills bacteria. Some of them have head with a tail sheath.
Bacteriophage
Advantages and Disadvantages of Viruses
Outline advantages and disadvantages of viruses
Advantages of viruses
- Viruses are used in developing vaccines, for example, vaccines for measles, polio and rubella are made from viruses that have been attenuated (weakened).
- Viruses are used as biological weapons to kill organisms.
- They are used as vectors in genetic engineering to transfer genes from one organism to another for improving or treating the defective genes.
- Bacteriophages are viruses that attack bacteria and hence they help in controlling infections and diseases.
- Viruses are used as biological weapons in wars and in biological pest control.
Disadvantages of viruses
- Most viruses cause diseases to both plants and animals. Plant disease such tomato mosaic, cassava mosaic and tobacco mosaic; and animal diseases e.g. measles, small pox, poliomyelitis and yellow fever are caused by viruses.
Kingdom Monera
This
kingdom is made up of organisms known as bacteria (singular:
bacterium). They are the most ancient and smallest organisms with a
cellular structure. They are mainly single celled. Bacteria occupy many
environments such as soil, dust, water and in the bodies of plants and
animals
Some
bacteria are found in hot springs where temperatures are 78ºC or more.
Others can withstand very low temperatures. Some are found in very deep
cracks in the ocean floor, at very high temperatures, about 360ºC
(extreme thermophiles).
General and Distinctive Features of the Kingdom Monera
Explain general and distinctive features of the kingdom monera
General characteristics of the kingdom monera
- They are mainly unicellular and very small.
- They are all prokaryotic (nucleus not bound by membrane)
- They reproduce by binary fission.
- Some members of the kingdom are autotrophs while others are heterotrophs
- They have cell wall made up of protein material and sometimes lipids.
- Some bacteria form spores during adverse conditions i.e. extreme conditions e.g. high or low temperatures, drought etc. The spores allow them to survive as they have very thick resistant walls.
- Some are aerobes while others are anaerobes.
- The genetic material (DNA) is scattered in the cytoplasm and they lack internal membrane bound organelles such as mitochondria, chloroplasts, golgi bodies etc.
Structures of the Representative Organisms of the Kingdom Monera
Describe structures of the representative organisms of the kingdom monera
General structure of the bacteria
- Bacteria have strong and rigid cell walls due to the presence of murein. The wall prevents the cell from bursting when it absorbs much water (as a result of osmosis).
- Bacterial cells are bounded by partially permeable membranes.
- Bacteria possess capsules which are slimy or gummy.They have flagella which aid motility of the bacteria. Motile bacteria can move in response to a certain stimulus i.e. tactic movement. Flagella can easily be seen by electron microscope.
- They have small self replicating circle of extra DNA called a plasmid.
General structure of bacterium
Forms of bacteria
Bacterial shape is an important aid to classification. There are four main shapes
Coccus (plural: cocci)
They are spherical in shape and can be of the following types.
- Micrococcus – exist singly. They cause sore throat.
- Diplococci - this type of bacteria exist in pairs. The pneumococci (Diplococcus pneumoniae) are the only members. They cause pneumonia.
- Streptococci – this type of bacteria stick together and form a chain. Most of them infect upper respiratory surface and cause diseases e.g. sore throat.
- Staphylococci – These bacteria form a grape like bunch. They cause boils, pneumonia, food poisoning and other diseases.
Bacilli (singular: bacillus)
These are rod shaped bacteria. They can be:
- Single rods, for example, Escherichia coli commonly living in the gut and Salmonella typhi which cause typhoid fever.
- Rods in chain, for example, Azotobacter, a nitrogen-fixing bacteria, and Bacillus anthracis which cause the disease anthrax.
- Bacilli with endospores showing various positions, shapes and sizes of spores. They can be:
- Central, not swollen e.g. Bacillus anthracis causes anthrax
- Spherical spore, terminal swollen e.g. Clostridium tetani causes tetanus
- Sub-terminal, swollen e.g. Clostridium botulism causes botulism.Spores may also be central
Spirilla (singular: spirillum)
These are spiral-shaped bacteria e.g. Treponema pallidum which causes syphilis
Sprrilla
Vibrio
These are comma shaped bacteria, for example Vibrio cholerae.
Vibrio cholerae
The Advantages and Disadvantages of the Kingdom Monera
Outline the advantages and disadvantages of the kingdom monera
Economic Importance of Bacteria
In Agriculture, the bacteria are mostly important for following reasons
- Nitrogen fixation:Plants cannot trap nitrogen from the atmosphere but bacteria can fix nitrogen and change it into nitrogenous compounds. The phenomenon is called nitrogen fixation. The bacteria, which fix atmospheric nitrogen, are called nitrogen-fixing bacteria. Some of the nitrogen fixing bacteria are found freely in soil are called free-living bacteria, eg. Clostridium and Azotobacter. Some of them are found in root nodules making association with leguminous plants called symbiotic bacteria, eg. Rhizobium.
- Nitrification:Some bacteria convert ammonium compounds into nitrates in the soil. The process is called nitrification. The bacteria that take part in this process are called nitrifying bacteria, eg. Nitrobacter and Nitrosomonas. Nitrosomonas NitrobacterAmmonia--------------->Nitrites------------->Nitrates
- Ammonification:Some bacteria utilize proteins of dead bodies and convert it into amino acids. These amino acids are converted into ammonia by some bacteria. The process is called ammonification and the bacteria involve in the process are called ammonifying bacteria. Then the ammonia reacts with CO2 and H2O and gives ammonium carbonate which is absorbed by plants.
- Bacteria decompose dead bodies. They convert complex organic compounds into simple inorganic compounds. Therefore they're called natural scavengers.
- Bacteria make the milk sour and produce flavor. They are responsible for coagulation of milk. E.g. Lacto bacillus.
- Bacteria convert sugary substances into alcohol, acids, acetones; etc the process is called fermentation.
- Bacteria also help to produce different types of enzymes like Amylase secreted from Bacillus, Protease from Bacillus, Streptokinase from Streptomyces.
- Bacteria are useful for vitamin production like Vitamin B (Cabalmin) is secreted from Pseudomonas, Vitamin B (Riboflavin) is secreted from Clostridium.
- They are important for antibiotic production like Terramycin from Streptomyces rimosus, Streptomycin from S. griseus, Neomycin from S. fradiae.
- They are also important to produce hydrogen commercially. During the process they ferment carbohydrate and hydrogen gas is produced.
- Bacteria decompose waste products.
Disadvantage of Bacteria
- Some of the species cause food poisoning. They secret some toxic chemical substances on out food stuff which cause food poisoning, eg Staphylococcus and Clostridium.
- Some are responsible for human diseases: Cholera: Vibrio cholera, Pneumonia: Staphylococcus pneumoniae, Diarrohea: Escherechia coli, Tuberclosis: Mycobacterium tuberclosis Leprosy: M. leprae, Meningitis: Nisseria meningitides.
- Some bacteria are responsible for plant diseases. Red stripe in sugarcane, Leaf streak in rice, black rot in cabbage and yellow rot in wheat are caused by Xanthomonas and Pseudomonas.
The Characteristics of Pathogenic and Non-pathogenic Bacteria
Outline the characteristics of pathogenic and non-pathogenic bacteria
Pathogenic bacteriaare bacteria that can cause infection. This article deals with human pathogenic bacteria.
Although
most bacteria are harmless or often beneficial, several are pathogenic.
One of the bacterial diseases with the highest disease burden is
tuberculosis, caused by the bacteriumMycobacterium tuberculosis,
which kills about 2 million people a year, mostly in sub-Saharan
Africa. Pathogenic bacteria contribute to other globally important
diseases, such as pneumonia, which can be caused by bacteria such asStreptococcusandPseudomonas, and foodborne illnesses, which can be caused by bacteria such asShigella,Campylobacter, andSalmonella.
Pathogenic bacteria also cause infections such as tetanus, typhoid
fever,diphtheria,syphilis, and leprosy. Pathogenic bacteria are also the
cause of high infant mortality rates in developing countries.
Nonpathogenic organismsare
those that do not cause disease, harm or death to another organism and
is usually used to describe bacteria.It describes a property of a
bacterium - its ability to cause disease. Most bacteria are
nonpathogenic. It can describe the presence of non-disease causing
bacteria that normally reside on the surface of vertebrates and
invertebrates as commensals. Some nonpathogenic microorganisms are
commensals on and inside the body of animals and are called microbiota.
Some of these same nonpathogenic microorganisms have the potential of
causing disease, or being pathogenic if they enter the body, multiply
and cause symptoms of infection.
Immunocomprised
individuals are especially vulnerable to bacteria that are typically
nonpathogenic but because of a compromised immune system, disease occurs
when these bacteria gain access to the body's interior. Genes have been
identified that predispose disease and infection with nonpathogenic
bacteria by a small number of persons.Nonpathogenic colistrains normally
found in the gastrointestinal tract have the ability to stimulate the
immune response in humans, though further studies are needed to
determine clinical applications.
Kingdom Protoctista
General and Distinctive Features of the Kingdom Protoctista
Explain general and distinctive features of the kingdom protoctista
This
Kingdom comprises of unicellular and simple multicellular organisms
whose cells have organized nucleus and membrane bound organelles. It
includes the algae and protozoa.
Algae
have chlorophyll hence make their own food through the process of
photosynthesis.Protozoa are heterotrophic taking in ready-made food.
Other
organisms, which are included in this Kingdom are red algae, Brown
algae, Amoeba, Euglena, plasmodium, trypanosome and paramecium.
General features of Kingdom Protoctista
- Some are autotrophs, for example Euglena while others are multicellular.
- They are all eukaryotes with most of them having locomotery structure.
- Most of them live in moist places or in water.
Distinctive features
- Most are unicellular eukaryotes
- They reproduce by binary fission
Phyla of the Kingdom Protoctista
Mention phyla of the kingdom protoctista
The phyla of kingdom protoctists include the following:
- Euglenophyta e.g. Euglena
- Rhizopodia e.g. Amoeba
- Zoomastigma e.g. Trypanosoma
- Apicomplexa e.g. Plasmodium
- Oomycota e.g. White root
- Chlorophyta e.g. Spyrogyra
- Cilliaphora e.g. Paramecium
- Rhodophyta e.g. Red algae
Structure of Amoeba and Paramecium
Describe structure of amoeba and paramecium
Amoeba belong to phylum Rhizopoda, organisms with the following extra features:
- They are eukaryotes
- Unicellular
- Parasitic
- They move using pseudopodia
Pseudopodia are projection of the cytoplasm that extend and pull the amoeba forward or engulf food particles.
The Advantages and Disadvantages of Amoeba, Euglena Paramecium and Plasmodiu
Explain the advantages and disadvantages of amoeba, euglena paramecium and plasmodium
Advantages of Paramecium:Are eaten by small water animals
Disadvantages of Paramecium:Causes diseases of bulanterdium eoli destroying the lining of intestines
Osmoregulation:Paramecium
has two contractile vacuoles and each is associated with permanent
system of collecting channels, which empty, into the main vacuole.
Feeding:Paramecium feed on bacteria. These are obtained from the surrounding water by the beating of the cilia-lining o the oral grove.
Reproduction:Paramecium
reproduces both asexually and sexually. The asexual method is more
common and it is binary fission. Sexual method is called conjugation.
Movementin paramecium is caused by cilia beating. This movement is called cilliary movement.
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