Unit No. 5: Variety of Life. In this first-year biology exploration, we embark on a captivating journey through the awe-inspiring world of taxonomy, evolution, and the intricate relationships that bind different species together. From the tiniest microorganisms to the grandeur of multicellular organisms, this unit delves into the classification, characteristics, and evolutionary history that have sculpted the remarkable variety of life forms that grace our biosphere. Through meticulous observation, analysis, and the pursuit of knowledge, we unravel the threads that weave the web of life, unlocking the secrets that define and differentiate the countless organisms with which we share this wondrous planet.
Unit 5 Biology of 1st Year Short Answers Questions
How many species of animals and plants are currently known?
Answer: Over one and a half million species of animals and over a half million species of plants are known.
Why is a systematic classification system necessary for dealing with such a large variety of species?
Answer: A systematic classification system is necessary to organize and categorize species in a meaningful way that reveals their relationships, differences, and similarities.
Why is classifying flowering plants based on color or height not considered meaningful?
Answer: Classifying flowering plants based on color or height is not meaningful because it doesn’t provide information about the fundamental differences and similarities among different individuals.
- 1st Year Biology Unit No.1 Introduction Notes
- 1st Year Biology Unit No. 2 Biological Molecules Notes
- 1st Year Biology Unit No. 3 Enzymes Notes
- 1st Year Biology Unit No. 4 The Cell Notes
- 1st Year Biology Unit No. 6 Kingdom Prokaryotae Notes
What is the basis of classification in biology?
Answer: Classification in biology is based on relationships among individuals, primarily similarity in form or structure. Biologists use homologies, comparative biochemistry, cytology, and genetics to classify living things into groups showing similarities.
How is a species defined, and why is “interbreeding” not a criterion for all organisms?
Answer: A species is defined as a group of natural populations that can interbreed freely among themselves, producing fertile offspring, while being reproductively isolated from other such groups in nature. “Interbreeding” cannot be used as a criterion for species recognition among predominantly asexually reproducing organisms.
What are some characteristics that differentiate species from one another?
Answer: Each species possesses distinct structural, ecological, and behavioral characteristics that set them apart from other species. They are considered independent evolutionary units that do not exchange genes with different species.
How have living things traditionally been divided into categories?
Answer: Living things have traditionally been divided into two kingdoms: plants and animals. Within each kingdom, further divisions like phyla (or divisions for plants, algae, and fungi) are made.
Describe the hierarchy of taxonomic categories from species to kingdom.
Answer: The taxonomic categories from species to kingdom form a hierarchy. It starts with species, then moves to genus, family, order, class, phylum, and finally kingdom. Each category is more general than the one below it and represents larger, more inclusive groups.
What is the purpose of taxonomic categories beyond species level?
Answer: Taxonomic categories beyond the species level allow for the grouping of organisms into larger, more inclusive categories (taxa), revealing broader relationships and properties that emerge as species are grouped together.
How is the concept of taxonomy demonstrated in the classification of corn?
Answer: In the classification of corn, the taxonomic hierarchy is evident, with corn being classified from kingdom to species. It demonstrates how organisms are categorized into increasingly specific groups based on their characteristics and relationships.
What is the significance of binomial nomenclature in biology?
Binomial nomenclature is a system of naming organisms using two words (generic name and specific name), devised by Carl Linnaeus. It provides a standardized and universally recognized way of identifying and classifying species.
How did common names for plants and animals lead to confusion?
Common names were inconsistent and varied by region, leading to confusion as the same species could have multiple names or a single name could refer to different species.
Who introduced the system of binomial nomenclature, and why was it important?
Carl Linnaeus introduced the system of binomial nomenclature. It was important because it provided a scientific and structured way to name and classify organisms, eliminating confusion caused by common names.
What does the first part of a scientific name represent in binomial nomenclature?
The first part of a scientific name in binomial nomenclature represents the genus to which the species belongs. It is called the generic name and starts with a capital letter.
How is the second part of a scientific name written?
The second part of a scientific name represents the species within the genus. It follows the generic name and starts with a lowercase letter.
How did Linnaeus choose the names for plants and animals in his binomial nomenclature system?
Linnaeus derived the scientific names from Latin words. Often, these names were based on characteristics of the organism or the person who collected it.
How did Linnaeus’s classification system evolve over time?
Initially, Linnaeus’s classification was based on the appearance or morphology of organisms. However, with advancements in fields like cytology, genetics, and molecular biology, the classification system has been modified to incorporate new knowledge.
Provide an example of a species with its complete scientific name using binomial nomenclature.
- Onion: Allium cepa
- Amaltas: Cassia fistula
- Human: Homo sapiens
Explain the concept of a generic name and a specific name in binomial nomenclature.
The generic name indicates the genus to which the species belongs and starts with a capital letter. The specific name indicates the particular species within the genus and starts with a lowercase letter.
Why did Carl Linnaeus replace common names with scientific names for classifying organisms?
Linnaeus replaced common names with scientific names to establish a consistent, universal, and standardized naming system for organisms that would eliminate confusion caused by regional variations in common names.
What were the initial two kingdoms in the early classification systems, and how were they defined?
The initial two kingdoms were plants and animals. Plants were defined as autotrophic organisms capable of preparing their own food through photosynthesis, while animals were defined as heterotrophic organisms that rely on other organisms for food.
Why did some biologists find the two-kingdom classification system problematic?
Some biologists found the two-kingdom system unworkable because it didn’t account for the diversity of unicellular organisms that exhibited both plant-like and animal-like characteristics, such as Euglena. Additionally, the system ignored the differences between prokaryotic and eukaryotic cells.
Who proposed the third kingdom called “Protista,” and why was it introduced?
Ernst Hackel proposed the third kingdom, Protista, to accommodate organisms like Euglena and bacteria that didn’t fit neatly into the existing plant and animal categories. Protista was introduced to address the complexity of certain unicellular organisms.
How did E. Chatton differentiate between prokaryotic and eukaryotic cells in terms of naming?
E. Chatton introduced the terms “prokaryotique” and “eu-cariotique” to differentiate between prokaryotic (bacteria and blue-green algae) and eukaryotic (animal and plant) cells. “Prokaryotique” means before the nucleus, referring to cells lacking a true nucleus, while “eu-cariotique” means true nucleus, referring to cells with a well-defined nucleus.
What is the main distinction between fungi and plants in terms of their nutritional strategy?
Fungi are heterotrophic organisms that obtain energy and structural materials by breaking down and absorbing food substances from their surroundings. In contrast, plants are autotrophic, meaning they can produce their own food through photosynthesis.
Describe the Five Kingdom Classification proposed by Robert Whittaker.
Robert Whittaker’s Five Kingdom Classification is based on three levels of cellular organization associated with three principal modes of nutrition: photosynthesis, absorption, and ingestion. The five kingdoms are:
- Monera (prokaryotic unicellular organisms like bacteria).
- Protista (eukaryotic predominantly unicellular organisms like Euglena and Amoeba).
- Plantae (eukaryotic multicellular autotrophs).
- Fungi (eukaryotic multicellular absorptive heterotrophs, like mushrooms).
- Animalia (eukaryotic multicellular consumers).
How did Lynn Margulis and Karlene Schwartz modify the Five Kingdom Classification?
Lynn Margulis and Karlene Schwartz modified the Five Kingdom Classification by considering cellular organization, mode of nutrition, cytology, genetics, and the presence of organelles of symbiotic origin (mitochondria, chloroplasts). They introduced additional criteria to classify organisms more accurately.
What was the original meaning of the word “virus” during the time of Louis Pasteur and Robert Koch?
The word “virus” was generally referred to as a poison associated with disease and death.
How is the present notion of a virus different from the earlier understanding?
The present notion of a virus recognizes it as particles of nucleic acid often with a protein coat. They replicate in living cells and cause diseases.
What branch of science deals with the study of viruses?
The branch that deals with the study of viruses is known as virology.
How can a virus be defined?
A virus can be defined as non-cellular infectious entities that contain either RNA or DNA encased in a protein coat. They reproduce only in living cells.
Who first developed an effective method of prevention against a viral disease, and how did they do it?
Edward Jenner was the first to develop an effective method of prevention against a viral disease. He vaccinated an 8-year-old boy with material from cowpox lesions and later exposed him to smallpox, but the boy did not develop the disease.
What term did Louis Pasteur use for inoculation against disease, and why?
Louis Pasteur used the term “vaccination” for inoculation against disease. The material he used was obtained from cows (Latin: vacca), hence the term.
How did Charles Chamberland contribute to our understanding of viruses?
Charles Chamberland discovered that bacteria cannot pass through porcelain filters, but the agent responsible for rabies could. He described these filter-passing agents as “filterable viruses.”
Who discovered that the agent causing tobacco mosaic disease was filterable and how did they prove it?
Ivanowski discovered in 1892 that the agent causing tobacco mosaic disease was filterable. He obtained a bacteria-free filtrate from infected plants and showed that it could transmit the disease to healthy plants.
When were the filterable agents first purified, and what did their chemical analysis reveal?
The filterable agents were first purified in 1935 by Stanley, who successfully crystallized the tobacco mosaic virus. Chemical analysis showed that they contained only nucleic acid and protein, suggesting their simple chemical composition.
Who independently discovered bacteriophages, and how did they describe them?
Bacteriophages, viruses that infect bacteria, were discovered independently by Twort in 1915 and D’Herelle in 1917. Twort observed bacterial colonies undergoing lysis, and D’Herelle used the term “bacteriophages” meaning “bacteria eater” to describe them.
What is the size range of viruses?
Viruses range in size from 250 nanometers (nm) for poxviruses to 20 nm for parvoviruses.
How do viruses compare in size to most bacteria?
Viruses are 10 to 1000 times smaller than most bacteria.
What is the structural characteristic that allows viruses to pass through filters that bacteria cannot?
Viruses are smaller than the pores of filters, allowing them to pass through.
Where can viruses reproduce?
Viruses can reproduce only in animal and plant cells or in microorganisms.
What is the process by which viruses reproduce within host cells?
Viruses reproduce through replication, forming many copies or replicas of themselves.
What is an obligate intracellular parasite?
A virus that can only replicate within host cells is called an obligate intracellular parasite.
What metabolic machinery do viruses lack for synthesizing nucleic acids and proteins?
Viruses lack the metabolic machinery for nucleic acid and protein synthesis.
What is the complete, mature, and infectious form of a virus called?
The complete infectious particle is known as a virion.
What are the two main components of a virion?
A virion consists of a central core of nucleic acid (DNA or RNA) and a surrounding protein coat called the capsid.
What gives definite shape to a virion?
The capsid, made up of protein subunits known as capsomeres, gives definite shape to a virion.
What is the envelope of a virus derived from?
The envelope of some viruses is derived from the host cell.
What are viruses without an envelope called?
Viruses without an envelope are known as naked virions.
What is the recently discovered microorganism responsible for mad cow infection and brain infections in humans?
Prions, which are infectious proteins, are responsible for these infections.
What sets prions apart from other microorganisms in terms of their genetic information?
Prions are composed of protein only and contain the information for their own replication, unlike other organisms that have genetic information in nucleic acids.
Which bacteriophages were mainly studied in earlier research, particularly those infecting Escherichia coli?
T phages, with T2 and T4 being well-known examples, were mainly studied in bacteriophage research.
What does the structure of a T4 bacteriophage resemble?
The structure of a T4 bacteriophage resembles that of a tadpole, with a head and a tail.
What is the main component of a bacteriophage head, and what is its shape?
The head of a bacteriophage contains a double-stranded DNA molecule and has an elongated pyramidal, hexagonal, prism-shaped structure.
What is the function of the tail fibers in a bacteriophage?
The tail fibers are structures for attachment to host cells.
What is the approximate volume of a bacteriophage compared to its host?
The volume of a bacteriophage is about 1/1000 of its host.
What is the initial step in the replication of a bacteriophage?
The initial step in the replication of a bacteriophage is its attachment (adsorption) to a host cell at a receptor site on the bacterial cell wall.
What happens during the attachment of a bacteriophage to a host cell?
During attachment, a weak chemical union takes place between the virion and the receptor site on the bacterial cell wall.
What enzyme is released during the penetration step of bacteriophage replication?
The enzyme lysozyme is released during the penetration step of bacteriophage replication.
How does the bacteriophage inject its DNA into the host cell?
The bacteriophage injects its DNA into the host cell through the tail core, similar to how a syringe is used to inject a vaccine.
What happens immediately after the viral nucleic acid enters the host cell?
The viral nucleic acid takes control of the host’s biosynthetic machinery and induces the host cell to synthesize necessary viral components (DNA, proteins) and start multiplying.
How are new bacteriophages formed, and when does bacterial cell lysis occur?
About 25 minutes after initial infection, approximately 200 new bacteriophages are formed, and the bacterial cell bursts, undergoing lysis.
What is the term for the phage that causes lysis of the host cell?
The phage that causes lysis of the host cell is known as a lytic or virulent phage.
What is the difference between a lytic phage and a temperate (lysogenic) phage?
A lytic phage causes the host cell to burst and undergo lysis, releasing new phages. A temperate (lysogenic) phage can incorporate its DNA into the host’s chromosome, leading to lysogeny, where the host continues to live and reproduce normally.
What is lysogeny in the context of bacteriophage replication?
Lysogeny is a process where the viral DNA becomes incorporated into the bacterial chromosome, and the host cell continues to live and reproduce normally with the viral DNA passing to each daughter cell.
What triggers the transition from lysogeny to the lytic cycle in a temperate phage?
The process called induction triggers the transition from lysogeny to the lytic cycle in a temperate phage. It involves the detachment of the viral DNA from the host’s chromosome.
What are the most important factors for classifying viruses?
Virus morphology and nucleic acid properties are the most important factors for classifying plant, animal, and bacterial viruses.
How is genetic material categorized in viruses?
The genetic material in viruses can be either DNA or RNA, and it can be naked, enveloped, or complex.
How are viruses classified based on morphology?
Viruses can be classified based on morphology into different shapes, such as rod-shaped (e.g., T.M.V), spherical (e.g., poliovirus), and tadpole-like bacteriophage viruses.
What is smallpox and what type of virus causes it?
Smallpox is a disease caused by pox viruses, which are DNA-enveloped viruses. It was a common disease until the early 20th century, characterized by raised fluid-filled vesicles that turn into pustules and form pitted scars.
What is herpes simplex, and which type of virus is responsible for it?
Herpes simplex is a disease caused by herpes viruses, which are DNA viruses. It leads to vascular lesions in the epithelial layers of ectodermal tissues, commonly occurring on the mouth and lips.
What are the characteristics of influenza viruses?
Influenza viruses are enveloped RNA viruses that cause a widespread disease in humans and occur in epidemic forms.
How are mumps and measles viruses classified?
Mumps and measles viruses belong to the group paramyxoviruses. They are large, enveloped RNA viruses.
What is the virus responsible for causing poliomyelitis?
Poliomyelitis is caused by the polio virus, which is a small RNA virus with a spherical capsid.
What is unique about retroviruses and their enzyme reverse transcriptase?
Retroviruses, including HIV, have a special enzyme called reverse transcriptase that can convert single-stranded RNA genomes into double-stranded viral DNA. This DNA can infect host cells and be incorporated into the host genome, potentially leading to the transformation of normal cells into cancer cells.
What were some of the complex symptoms observed in young males affected by the disease in the early 1980s?
Severe pneumonia, rare vascular cancer, sudden weight loss, swollen lymph nodes, and general loss of immune functions.
Who were the initial patients reported to have this disease?
Homosexual individuals.
What was the major cell infected by the human immunodeficiency virus (HIV)?
Helper T-lymphocytes.
What happens as the HIV infection progresses in the host?
The decrease of helper T-lymphocytes leads to the failure of the immune system, making the infected person susceptible to other diseases.
How is HIV transmitted?
Through intimate sexual contact, contact with blood, breast feeding, and sometimes through professional activities such as healthcare work.
What are the methods of preventing HIV transmission?
Avoiding direct contact with HIV, using sterile needles/syringes, and practicing safe sexual behaviors.
When did the experimental administration of an HIV vaccine in humans begin?
Early 2001 in South Africa.
What is hepatitis?
Inflammation of the liver, often caused by viral infection, toxic agents, or drugs.
What are some common symptoms of hepatitis?
Jaundice, abdominal pain, liver enlargement, fatigue, and sometimes fever.
Which types of viral hepatitis are better known?
Hepatitis A, B, and C.
How is hepatitis A (HAV) transmitted?
Through contact with feces from infected individuals.
How is hepatitis B (HBV) transmitted?
Through the exchange of body fluids, such as blood serum, breast milk, and saliva, as well as from mother to child during birth or afterward and by sexual contact.
What are some ways to control hepatitis?
Adopting hygienic measures, routine vaccination, and screening of blood/organs/tissues from donors.
Is there a genetically engineered vaccine available for hepatitis B (HBV)?
Yes.
Is there a vaccine available for hepatitis C (HCV)?
No.
Unit 5 Biology of 1st Year Long Answer Questions
Describe the structure of Bacteriophage?
A bacteriophage is a type of virus that infects and replicates within bacteria. It has a complex structure consisting of several components that allow it to attach to a bacterial host, inject its genetic material, and take over the host’s cellular machinery for reproduction. Here’s a description of the structure of a typical bacteriophage:
Head or Capsid: The head is the proteinaceous outer shell that encases the bacteriophage’s genetic material. It is often polyhedral in shape and composed of protein subunits arranged in a geometric pattern.
Tail: The tail is a long, tubular structure that extends from the head. It is involved in the attachment to the bacterial host and the injection of the phage’s genetic material into the host cell.
Base Plate: The base plate is located at the end of the tail and serves as a connection point between the tail and the head. It often contains protein fibers or spikes that help the phage attach to specific receptors on the bacterial cell surface.
Tail Fibers: These are thin proteinaceous structures extending from the base plate. They play a crucial role in recognizing and binding to specific receptor molecules on the bacterial cell surface. The interaction between tail fibers and bacterial receptors determines the host specificity of the bacteriophage.
Sheath: The tail sheath is a contractile structure within the tail that contracts upon attachment to the bacterial cell. This contraction generates the force required to inject the phage’s genetic material into the host.
Genetic Material: The genetic material of a bacteriophage can be either DNA or RNA, depending on the type of phage. This genetic material carries the instructions necessary for the replication and assembly of new phage particles inside the bacterial host.
Tail Pins: These are thin structures that connect the base plate to the tail sheath. They help stabilize the tail structure and guide the tail sheath during contraction.
Collar: The collar is a ring-like structure located at the junction between the head and the tail. It aids in the transfer of genetic material from the head to the tail during the injection process.
The life cycle of a bacteriophage typically involves attachment and binding to the bacterial host, injection of the genetic material into the host cell, replication and assembly of new phage particles, and finally, lysis of the bacterial cell to release the newly formed phages. This lysis is often visible as clear spots on a bacterial lawn, a phenomenon known as a “plaque.” Bacteriophages have been extensively studied and have played a significant role in advancing our understanding of genetics, molecular biology, and viral replication processes.