Introduction to Biology notes
MDCAT Biology
Biology is the study of life and living organisms. This chapter introduces the major fields of biology, scientific reasoning, biological organization from bioelements to biosphere, and selected applications such as breeding, cloning, cancer treatment, industrialization, and environmental studies.
Biology and Its Major Divisions
Biology is the scientific study of living organisms. It includes the study of their structure, functions, classification, development, heredity, evolution, and relationships with the environment.
The broad fields of biology are zoology, botany, and microbiology. Zoology deals with animals, botany deals with plants, and microbiology deals with microscopic organisms such as bacteria, some fungi, protozoans, and viruses. Modern biology is further divided into many specialized branches.
- Zoology: the study of animals.
- Botany: the study of plants.
- Microbiology: the study of microscopic organisms.
- Morphology: the study of the external form and features of organisms.
- Anatomy: the study of the internal structure of organisms.
- Physiology: the study of the functions of body parts.
- Cell biology or cytology: the study of cells and their components.
- Histology: the study of tissues.
- Genetics: the study of heredity and variation.
- Embryology: the study of development from fertilization to the formation of an embryo.
Fields Related to Organisms and Their Environment
Some branches study organisms according to their habitat, relationships, or way of life. These fields help scientists understand how organisms are distributed and how they interact with one another and with non-living factors.
Environmental biology deals with living organisms in relation to their environment. Ecology is closely related to this field and studies interactions among organisms and between organisms and their surroundings.
- Freshwater biology: the study of organisms living in freshwater bodies such as rivers, lakes, and ponds.
- Marine biology: the study of organisms living in seas and oceans.
- Parasitology: the branch of biology that deals with parasites and their relationships with hosts.
- Environmental biology: the study of living organisms in relation to their environment.
- Biogeography: the study of the distribution of organisms on Earth.
- Paleontology: the branch of biology used for the identification and interpretation of fossils.
- Fossils are preserved remains, impressions, or traces of past organisms.
- The distribution of organisms can be studied through biomes, which are large ecological regions with characteristic climate, vegetation, and organisms.
Applied Fields of Biology
Biology is applied to medicine, agriculture, industry, and the protection of the environment. Applied biological fields use biological knowledge to solve human problems.
Biotechnology uses organisms, cells, or biological molecules to make useful products. It includes genetic engineering, tissue culture, fermentation, vaccine production, and some methods of diagnosis and treatment.
- Biotechnology: the use of organisms, cells, or biological processes for human benefit.
- Genetic engineering: the deliberate alteration of an organism's genetic material.
- Plant and animal breeders develop new methods through selective breeding, hybridization, and genetic engineering.
- Poultry farming uses biological knowledge to produce eggs and meat efficiently.
- A broiler is a chicken bred and reared mainly for meat production. It is a common source of quick and relatively cheap white meat.
- Pharmacology: the study of drugs and their effects on living organisms.
- Immunology: the study of the immune system and immunity.
- Industrial biology applies biological processes in industries such as food production, fermentation, and medicines.
Biology, Medicine, and Industrialization
Medical biology applies biological knowledge to the prevention, diagnosis, and treatment of disease. Cancer may be treated by methods such as surgery, radiotherapy, chemotherapy, immunotherapy, or targeted treatment, depending on the type and stage of cancer.
Antibiotics act against susceptible bacteria. They are not general cancer treatments. Antisepsis is also different from antibiotic treatment because it refers to reducing or eliminating microorganisms on living tissue using a chemical substance.
- Antisepsis: the elimination or inhibition of bacteria and other microorganisms on a living surface by using a chemical substance.
- Disinfection refers to the treatment of non-living objects and surfaces to destroy or reduce harmful microorganisms.
- Antibiotics are substances used against certain bacteria. They do not treat cancer.
- Cancer treatments may include surgery, radiotherapy, chemotherapy, and immunotherapy.
- Industrialization can increase production, provide useful products, and support economic development.
- Industrialization may also cause pollution, habitat destruction, waste production, and depletion of natural resources.
- Biology helps reduce industrial damage through waste treatment, pollution control, conservation, and environmental monitoring.
Scientific Reasoning in Biology
Biologists use observation, questioning, reasoning, experimentation, and evidence. Scientific reasoning may be deductive or inductive. Both forms help in developing and testing explanations.
Deductive reasoning begins with a general statement and reaches a particular conclusion. For example, if all birds have wings and sparrows are birds, then sparrows have wings. Inductive reasoning begins with specific observations and develops a general conclusion.
- Observation is the careful collection of information using the senses or scientific instruments.
- A hypothesis is a testable proposed explanation for an observation or problem.
- A hypothesis may result from deductive reasoning or may be suggested by observations, previous knowledge, or inductive reasoning.
- Deductive reasoning: general statement to a specific conclusion.
- Inductive reasoning: specific observations to a general conclusion.
- A prediction is a logical expected result based on a hypothesis.
- An experiment tests a hypothesis under controlled conditions.
- A scientific hypothesis must be testable and should be capable of being supported or rejected by evidence.
Levels of Biological Organization
Living matter is arranged in levels, from simple chemical components to complex ecological systems. Each higher level is formed by the organization and interaction of lower levels.
The cellular level begins with organelles and cells. Groups of similar cells form tissues. Different tissues combine to form organs, and organs work together in organ systems. An organism is a complete individual living system.
- Bioelement: an element required by living organisms. Common examples include carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulphur.
- Oxygen is the most abundant bioelement in living matter, while carbon is the second most abundant bioelement in the usual FSc description.
- Molecule: two or more atoms joined by chemical bonds.
- Organelle: a specialized structure inside a cell that performs a particular function.
- Cell: the basic structural and functional unit of life.
- Tissue: a group of similar cells performing a particular function.
- Cartilage is a connective tissue.
- Organ: a body part that forms a structural and functional unit and is composed of more than one tissue.
- Organ system: a group of organs that work together to perform a major function.
- Organism: an individual living thing.
Higher Levels: Population to Biosphere
Organisms do not live separately from one another. Individuals of the same species form populations, and populations of different species live together in communities. These communities interact with the non-living environment in ecosystems.
The levels above the organism explain relationships at large scales. A biosphere includes all regions of Earth where life exists.
- Species: a group of similar organisms that can generally interbreed and produce fertile offspring.
- Population: members of one species inhabiting the same area.
- The number of rats in a field of rice is an example of a population.
- Community: all the populations of different species living and interacting in an area.
- Ecosystem: a community together with its non-living environment.
- Biome: a large regional ecosystem characterized mainly by climate, vegetation, and typical organisms.
- Biosphere: the part of Earth where life exists, including parts of the atmosphere, hydrosphere, and lithosphere.
- The sequence of organization is: organelle, cell, tissue, organ, organ system, organism, population, community, ecosystem, biome, biosphere.
Reproduction, Cloning, and Biological Diversity
Reproduction produces new individuals and allows a species to continue. Sexual reproduction usually involves male and female gametes and produces genetic variation. In flowering plants, the flower is the reproductive organ involved in producing the next generation sexually.
A clone is produced asexually from one cell or individual. Clones are genetically very similar to the original organism, although environmental conditions can cause differences in their appearance or performance.
- The flower is the plant organ involved in sexual reproduction and production of the next generation.
- A clone is a cell or individual and its entire asexually produced offspring.
- Cloning may be used to reproduce organisms with desirable characteristics, produce medicines, preserve valuable genetic material, or study development.
- Cloning could also raise ethical, health, and biological diversity concerns.
- Several species have been cloned, including mammals and other animals. In the textbook context, the species cloned so far include all the listed examples.
- Selective breeding changes populations by choosing parents with desirable characteristics.
- Hybridization is the crossing of genetically different individuals to combine useful characteristics.
Organ Systems and Selected Biological Facts
An organism contains specialized organs and organ systems. The structure of an organ is related to its function. The skin is an organ and forms the outer protective covering of the human body.
The body also contains connective tissues, epithelial tissues, muscular tissues, and nervous tissue. These tissues combine in different ways to form organs.
- Skin is the largest organ of the human body.
- Skin protects the body, reduces water loss, detects stimuli, and helps regulate temperature.
- Cartilage is a flexible connective tissue found in structures such as the nose, external ear, and surfaces of some joints.
- A tissue is made of cells with a common function, while an organ contains more than one type of tissue.
- Animals form a major part of the known living diversity. The textbook figure associated with known animal species is 19.9 percent.
- Biological classification helps identify organisms and shows relationships among groups.
- Knowledge of biological organization connects the study of cells, tissues, organs, organisms, populations, and ecosystems.
Key terms
- Biology
- The scientific study of living organisms and their life processes.
- Freshwater biology
- The study of organisms living in freshwater bodies such as lakes, ponds, and rivers.
- Parasitology
- The branch of biology concerned with parasites and their hosts.
- Paleontology
- The study, identification, and interpretation of fossils.
- Environmental biology
- The study of living organisms in relation to their environment.
- Biotechnology
- The use of organisms, cells, or biological processes to produce useful products or services.
- Antisepsis
- The chemical elimination or inhibition of microorganisms on a living surface.
- Hypothesis
- A testable proposed explanation for an observation or problem.
- Deductive reasoning
- Reasoning that moves from a general statement to a specific conclusion.
- Inductive reasoning
- Reasoning that uses specific observations to form a general conclusion.
- Bioelement
- An element required by living organisms for their structure or functions.
- Cell
- The basic structural and functional unit of life.
- Tissue
- A group of similar cells that performs a particular function.
- Organ
- A structural and functional body unit made of more than one tissue.
- Population
- Members of one species living in the same area.
- Ecosystem
- A community of organisms together with its non-living environment.
- Biome
- A large ecological region with a characteristic climate, vegetation, and animal life.
- Clone
- A cell or individual and its asexually produced offspring, usually genetically similar to the original.
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Biology shortcuts
Recognising acellular organisms
If an entity has no cellular organisation and depends on a host for replication, identify it as a virus. Viruses are non-cellular and are not placed among cellular organisms.
- Check whether it has cytoplasm, ribosomes and independent metabolism.
- Viruses contain nucleic acid inside a protein coat but lack cellular structure.
- Example: An infectious particle without cytoplasm or ribosomes is a virus.
- Answer: Non-cellular virus.
This shortcut does not apply to bacteria, which are cellular prokaryotes.
Separating prokaryotic and eukaryotic cells
Use ribosomes as the common feature. Both cell types have ribosomes, but only eukaryotes have a membrane-bound nucleus and membrane-bound organelles.
- Look for the feature present in both groups.
- Ribosomes occur in prokaryotes and eukaryotes for protein synthesis.
- Example: Which structure is common to both? Ribosomes.
- Answer: Ribosomes.
Do not use mitochondria, chloroplasts or a membrane-bound nucleus as common features.
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