Class 01 Characteristics of Life

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Introduction to Life Sciences
LRA 302
Ahmed Osman, PhD.
Professor pf Biochemistry
Reference for Class – 1
Inquiry into Life
Twelfth Edition, 2007
Sylvia S. Mader
Chapter 1
The Characteristics of Life
• Earth possesses a great
variety of diverse life forms.
• All living things have certain
characteristics in common.
Common Characteristics
• Biochemical unity underlies the common
features at the biochemical level of the
greatly diverse biological world.
• Examples include DNA, a type of
macromolecule that stores genetic
information in all cellular organisms. It
consists of the same 4 building units in all
living cellular organisms. Another example
is represented by proteins, another type of
macromolecules that are key participants
in most biological processes. Proteins are
built from a set of 20 building blocks that
are the same in all organisms.
Common Characteristics
• Key metabolic processes, such as the
chemical conversion of glucose and oxygen
to CO2 and water as part of energy
production mechanism in living organisms,
are essentially the same in all living
organisms from bacteria through human.
• Normal Biochemical Processes are the basis
of health.
• Any deviation from normal biochemical
processes results in a disease condition. In
addition, biochemical investigations and
laboratory tests contribute to the diagnosis
and treatment of many diseases.
Living Things:
• What characterize living things?
Living Things:
•
•
•
•
•
•
•
Are organized
Acquire materials and energy
Reproduce
Respond to stimuli
Are homeostatic
Grow and develop
Have the capacity to adapt
Adaptation
Long term / evolution / natural selection
Short term
Give example
Classification of Living Things
• Living organisms are assigned to groups
based upon their similarities.
Classification of Living Things
• Systematics
Identifying and classifying organisms.
Domains
• Domains are the highest level of
classification.
• Three domains
• Based on biochemical and genetic
evidence.
Domain Archaea
• Archaea are singlecelled organisms that
lack a membranebound nucleus.
• Archaea can be found
in environments that
are too hostile for
other life forms.
Domain Bacteria
• Bacteria are singlecelled organisms that
lack a membranebound nucleus.
• Bacteria are found
almost everywhere on
the planet Earth.
Prokaryotic / Bacterial cell
Archaea + Bacteria
=
Prokaryotes
Domain Eukarya
• The cells of all eukaryotes have a membranebound nucleus.
• Members of the Domain Eukarya are further
categorized into one of four Kingdoms.
Eukaryotic cell (Plant cell)
Eukaryotic cell (Plant cell)
 A large central vacuole (enclosed by a
membrane, the tonoplast), which maintains the
cell's turgor and controls movement of molecules
between the cytosol and sap
 A cell wall made up of cellulose and protein, and
in many cases lignin, and deposited by the
protoplast on the outside of the cell membrane;
this contrasts with the cell walls of fungi, which
are made of chitin, and prokaryotes, which are
made of peptidoglycan
 The plasmodesmata, linking pores in the cell
wall that allow each plant cell to communicate
with other adjacent cells; this is different from
the network of hyphae used by fungi
 Plastids, especially chloroplasts that contain
chlorophyll, the pigment that gives plants their
green color and allows them to perform
photosynthesis
 Plant groups without flagella (including conifers
and flowering plants) also lack centrioles that are
present in animal cells.
Eukaryotic cell (Animal cell)
Domain Eukarya
Categories of Classification
Domain
Kingdom
Phylum
Class
Order
Family
Genus
species
Categories of Classification
Domain
Kingdom
Phylum
Class
Order
Family
Genus
species
Most inclusive
Least inclusive
Systematic position of Humans
Domain?
Kingdom?
Systematic position of Humans
Scientific Names
• Binomial (two names)
– Genus name, species name
–Examples:
»Homo sapiens (human)
»Felis domesticus (domestic cat)
• Carl Linnaeus;
The father of modern taxonomy, he was a Swedish botanist,
physician, and zoologist who formalised binomial nomenclature.
• Systema Naturae, published 1735; 10th ed.1758.
Organization of the Biosphere
• Biosphere
• Zone of air, land, and water at the surface of the
Earth where living organisms are found.
Organization of the Biosphere
• Ecosystem
(interactions btw communities and the
physical habitat)
• Community (interacting populations)
• Population (a species in a given area)
Ecosystems
Ecosystems are characterized by:
Chemical cycling
Energy flow
Role of Climate
Biodiversity
• Total number of species
• Genetic variability
• Ecosystems diversity
Species Diversity
• about 30 million species on Earth
• < 2 million identified
• Earth is losing about 400 species per day
due to human activities
• Overfishing, habitat destruction, species
introductions
The
Scientific
Method
Observation
Experimental Design
experimental group selection
control group (placebo)
sample size
statistical analyses
Scientific Theory
• A scientific theory is a concept supported
by a broad range of observations,
experiments, and conclusions.
• This in contrast to commonly used “theory”
Examples of Theories in Biology
•
•
•
•
•
Cell
Homeostasis
Gene
Ecosystem
Evolution
The principles of “…” = accepted theory
The Process of Science
A Controlled Study
• Experiments have two types of groups:
• Experimental Group
• Control Group
The Process of Science
A Controlled Study
• Two Variables
– Experimental / independent variable
factor being tested.
– Response / dependent variable
result or change that occurs.
Science and Social
Responsibility
• Technology is the application of
knowledge for a practical purpose.
• Drugs for diseases
• Methods to detect / control cancer
• Increased agricultural production
Science and Social
Responsibility
• Technology has both benefits and drawbacks.
• Nitrogen fertilizers and eutrophication
• Pesticides
Science and Social
Responsibility
• Ethical and moral issues surrounding the use of
certain technologies must be decided by
societies.
• GMOs
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