Biology – Premed 1 Windsor University School of Medicine Dr Biology – Premed 1 Windsor University School of Medicine Dr. Veipu January 2015

Biology: The Science of Life

Biology is the science that studies living organisms: What they are? How they work? How they interact? How they evolve?

Response to the environment

Living things reproduce their own kind

How does a single tiny cell become a Tree?

Study of life extends from a global scale of the planet earth to the microscopic scale of cells and molecules Biosphere –> Ecosystem –> Community Population –> Organisms –> Organs Tissues –> Cells –> Organelles –> Molecules

Individual living things are “Organisms”

All organisms share basic characteristics from a single-cell to a complex human Basic features of living organisms are: 1. Highly organized and complex entities formed of one or more cells; 2. Carry out and control numerous chemical processes; 3. Acquire and use energy for metabolism; 4. Respond to changes in environment and maintain a constant internal environment; 5. Grow in size, develop; 6. Produce offspring similar to them; 7. Adapt to environmental changes and gradually evolve into new type of organisms.

Diversity of Life

Millions of organisms exist on earth --- Plants, animals, bacteria and viruses Techniques have been developed for identification, naming and grouping of various organisms --- Biological Classification or “Taxonomy”

Taxonomy enfolds the following fundamental element: Nomenclature --- Assigning of names to organisms based on the degree to which they share characteristics Nomenclature can vary from one discipline to another, therefore a scientific name that is acceptable universally must identify and organism

Guidelines for Naming of Organisms: (i) A scientific name generally has two words in Latin or derived from Latin irrespective of their origin (ii) First word denotes the genus whereas the second one is for species (iii) Names are printed in italics or are separately underlined to indicate their Latin origin (iv) Generic name starts with a capital letter and the specific name with a small letter e.g. mangifera indica (v) The name of the author is written in abbreviated form after the species name and is printed in Roman e.g. Mangifera indica Linn. (vi) Each taxonomic group can have only one correct name (vii) The name should be short, precise and easy to pronounce

Carolus Linnaeus (1707-1778), Swedish naturalist, referred to as “Father of Taxonomy” First to propose an orderly system of classification of organisms Linnaeus introduced a system of nomenclature of plants and animals known as “Binomial Nomenclature”

According to binomial nomenclature, the scientific name of a species consist of 2 parts; first part represents genus to which the species belongs; second part represents the identity of the species to which the individual belongs E.g. Homo Sapiens E.g. Pisum sativum ( Pea plants)

Taxonomic Hierarchy To assign an organism an appropriate place in a system framework of classification Taxonomic groups are arranged in a definite order from Higher to Lower categories

Taxonomic Hierarchy The categories used in the classification of animals and plants: Kingdom (Highest) Phylum or Division Class Order Family Genus Species (Lowest) As we go from the lowest rank species towards kingdom the number of similar characteristics decreases

Decreasing Specificity Increasing Specificity

SPECIES – Basic unit for understanding taxonomy as well as evolution Group of individuals with similar morphological characters, which are able to breed among themselves and produce their own kind KINGDOM – All organisms that share a set of distinguishing common characters Plants are placed in Plant Kingdom while animals are placed in Animal Kingdom. This is the highest category of classification. **Higher the category, lesser will be the number of common characteristics of organisms belonging to that category

Various other systems of classification were proposed from time to time: Artificial System -- Classification based on one or a few superficial similarities such as shape or prominent features. Another example would be categorizing into (i) can fly and (ii) cannot fly Criteria considered for this type of grouping was simple and easy to follow Natural System -- Classification based on natural affinities and uses more number of characters rather than a single character for determining the similarities.

Phylogenetic System – Based on evolutionary sequence as well as the genetic relationships among the organisms Based on Darwin’s concept of Natural selection Development of group of organisms or even an organism from its origin to the present state

Five Kingdom Classification Monera Protista Fungi Plantae Animalia

Criteria for classifying into five kingdoms are complexity of cell structure, body organization, mode of nutrition, life style and the phylogenetic relationships All multi-cellular, mobile, and heterotrophic organisms were assigned the Kingdom Animalia Photosynthetic multi-cellular organisms were included in the Kingdom Plantae Unicellular plants like algae and protozoans were taken out of the plant and animal kingdom and were included in a separate Kingdom Protista Bacteria and multicellular blue green algae with prokaryotic cells were transferred from plant kingdom to a new kingdom called Monera

1. Kingdom Monera (Prokaryotes) Single-celled prokaryotic organisms like bacteria and photosynthetic blue green algae, and cyanobacteria Nucleus and other organelles do not have enclosing membranes Found in places like deep ocean floor, hot deserts, hot springs, survive in extreme temperatures, acidic/alkaline pH Survive in anaerobic oxygen free conditions called Eubacteria (also known as “true bacteria”) and Archaebacteria (“ancient bacteria) Bacteria are single-celled and take many form of shapes, good decomposers and help in recycling of nutrients

2. Kingdom Protista Both unicellular and multicellular organisms found in aquatic habitats Algae (photosynthetic activity) and protozoa (e.g. Amoeba, Paramecium) Membrane bound nucleus and may have cilia or flagella for their movements

3. Kingdom Fungi Fungi grow on decaying organic matter in moist and warm conditions Can be single-celled (Yeasts) and also multi-cellular complex filamentous structures (Mycelia) Reproduce by asexual spores or sexual reproduction

4. Kingdom Plantae Multi-cellular and photosynthetic forms of green plants Rigid cellulose cell wall which prevents contraction Lack locomotion Photosythesis process by which the green plants synthesize food by utilizing water, minerals, and carbon dioxide with the help of green pigment chlorophyll and solar energy

5. Kingdom Animalia: Multi-cellular eukaryotes No cell wall Depend on plants for their basic requirements of food Great diversity compared to other kingdoms

Microbiology --- Study of microscopic forms of life Genetics --- Study of inheritance of organisms Evolution --- Study of living systems as they change through time Ecology --- Study of the relationships of organisms to their physical environment in which they live and to one another Histology--- Study of the structural organization of living things at tissue level Physiology --- Study of the normal functioning of animals and plants during life Plant physiology --- Study of photosynthesis and transpiration Cytology --- Study on the structure and composition of cells Cell Biology --- Study correlating the structure of cells with their function Molecular Biology --- Study of the composition of the organic and inorganic molecules of the cells and their interactions Exobiology --- Study of life outside earth and within the solar system Ethology – Study of animal behavior based on the observation, recording and analysis of how animals function