Biology Premed 1 Windsor University School of Medicine Dr.
Veipu January 2015
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Biology: The Science of Life
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Biology is the science that studies living organisms: What they
are? How they work? How they interact? How they evolve?
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Response to the environment
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Living things reproduce their own kind
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How does a single tiny cell become a Tree?
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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
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Individual living things are Organisms
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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.
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Diversity of Life
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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
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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
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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
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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
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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)
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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
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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
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Decreasing Specificity Increasing Specificity
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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
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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.
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Phylogenetic System Based on evolutionary sequence as well as
the genetic relationships among the organisms Based on Darwins
concept of Natural selection Development of group of organisms or
even an organism from its origin to the present state
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Five Kingdom Classification Monera Protista Fungi Plantae
Animalia
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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
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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
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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
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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
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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
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5. Kingdom Animalia: Multi-cellular eukaryotes No cell wall
Depend on plants for their basic requirements of food Great
diversity compared to other kingdoms
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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