Biology 1116 Lecture Notes
Chapter 1: Biology: Exploring Life
- Lifes levels of organization define
the scope of biology
- Living organisms and their environments form
- Cells are an organism's basic unit of structure
- Unity in diversity: all forms of life have
- Biological diversity can be arranged into
- Evolution explains the unity and diversity
- Scientists use two main approaches to learn about nature
- Biology is connected to our lives in many
Lifes levels of organization
define the scope of biology
- Life is organized into several structural levels forming a hierarchy.
Biology is the scientific study of all these hierarchical levels of
biological organization (Fig 1.1)
- Ecosystem (biotic and abiotic components of a particular area)
- Community (all organisms in a particular area)
- Population (all individuals of a particular species in a particular
- Organ systems
- Cell (basic unit of living matter)
- Subatomic (electrons, protons and neutrons)
- Lifes hierarchy builds from molecules to ecosystem.
- Most biologists specialize in the study of life at a particular level.
- The deepest insights into biology often come from discovering connections
between various levels in the hierarchy of life.
- Each level in natures hierarchy has unique structures, and
a set of functional properties result from that structure.
- Each level has "emergent properties"
which are not present at lower levels. Emergent properties arise from
the interaction of component parts: The whole is greater than the
sum of its parts.
Living organisms and their environments
form interconnecting webs
- At highest level in natures hierarchy (the ecosystem) interactions
between organisms make up a web of relationships connecting all organisms
and the components of the environment.
- Environment = everything external
to organism (or gene). Includes both biotic
and abiotic factors.
- Fig 1.2: Highlights differences between
flow of chemical nutrients and flow of energy within an ecosystem.
- Energy flows through an ecosystem. In contrast, chemical
nutrients are cycled in an ecosystem.
- Ecosystems gain and loose energy constantly.
- Ultimately all energy entering an ecosystem is derived from the
sun by photosynthesis. All energy eventually leaves an ecosystem
as heat (this energy can not be harnessed to do useful work).
- Primary producers: includes
plants, algae, and some bacteria (Photosynthetic).
- Primary consumers: Animals
and protists that eat primary producers.
- Secondary consumers: eat primary
- Decomposers: Fungi and bacteria.
Nutrient recycling is essential.
- The web of relationships among plants, animals, microorganisms, and
the physical environment give an ecosystem structure (structure as applied
to an ecosystem is more abstract than that of physical entities).
- Interactions account for the passage of chemical nutrients and energy
throughout the ecosystem.
CELLS ARE AN ORGANISM'S BASIC UNITS OF STRUCTURE
- The cell is the lowest level of structure capable of performing all
the activities of life. Fundamental unit of life.
- Cell theory (Shleiden and Schwann): All
living things consist of cells, and all cells are derived from preexisting
cells. Ability of cells to divide to form new cells
is the basis for all reproduction and development.
- All cells are enclosed by a membrane which regulates passage of
materials between the cell and its surroundings.
- All cells have DNA at some point in their life cycle. DNA,
an information encoding molecule, is the heritable material that
directs the cell's activities.
- Two major kinds of cells (based on structural organization):(Fig
- Prokaryotes: includes
eubacteria, and archaea. Lack internal compartmentalization.
Simpler in structure. Very small.
- Eukaryotes: Have
extensive compartmentalization due to presence of organelles.
Larger and more complex than prokaryotes.
Unity in diversity: all forms of life
have common features
- Life on earth is monophyletic:
we all share a common ancestor. Lifes diversity is united by common
features whose foundation resides in the genetic information in DNA.
- Some common features of all life (Fig 1.4).
- Composed of one or more cells.
- all cells are DNA based (4 nucleotides)
- Universal genetic code. Specifications differ but not the language.
Information in DNA underlies all properties that distinguish life
- Ability to reproduce. Reproduction underlies the capacity of species
to evolve (i.e. change through time).
- Evolution and natural selection.
- Order: all living things exhibit highly ordered complex organization.
- Homeostasis: ability to keep internal environment constant,
despite external environmental fluctuations.
- Response to external stimuli.
- Growth and develepoment
- Energy utilization
- Evolutionary connections among all life forms account for the paradox
of unity in diversity.
Biological diversity can be arranged
into 3 domains
- A hallmark of life on earth is its incredible diversity. There are
tens of millions of species.
- To make the enormous diversity of life more comprehensible, taxonomists have devised ways of grouping organisms.
- Because organisms are grouped according to their similarities, taxonomy
often reflects evolutionary history.
- The tree of life has three main branches (Domains)
- 1. Bacteria
- most ancient, diverse, and ubiquitous.
- lack internal compartmentalization i.e.no nucleus nor membrane-bound
- 2. Archaea
- inhabit extreme habitats.
- thermophiles, halophiles, methanogens
- most closely related to Eukaryotes.
- 3. Eukarya
- includes protists, algae, plants, fungi, and animals
- cells contain a nucleus + membrane-bound organelles.
- Each Domain is divided into kingdoms. E.g. Domain eukarya contains
various kingdoms Protista, Fungi, Plantae, and Animalia.
Evolution explains the unity and diversity
Darwin: 1859 published "On the Origin of Species
by Means of Natural Selection".
- Theory of evolution by Natural Selection has revolutionized biology.
Provides a framework with great explanatory power. Unifies all disciplines
- Biology without evolution does not make sense.
- Natural Selection (Fig
- Occurs as heritable variations are exposed to environmental factors
that favor the reproductive success of some individuals over others.
- Results from responses of organisms to interactions with biotic
and abiotic factors in environment.
- Note: populations and species evolve, but not individuals. Evolution
is the change in "allele" frequencies over time.
- Adaptations = Set of features
evolved by natural selection enabling organisms to be well suited to
their particular environment.
Scientists use two main approaches to learn about nature
- Science is a way of knowing. It's an investigative process which can
be applied to almost any discipline. Biology is the scientific investigation
into the workings of nature at all levels of organization.
- Two main approaches used:
- Discovery science: Mostly descriptive (e.g sequencing of human genome, describing newly discovered species, etc...). Uses inductive reasoning (derivation general principles from large number of specific observations).
- Scientific method. 5 key elements:
- 1. Observations
- from others or results from previous experiments.
- 2. Questions
- about unclear aspects of observations: How? When? Why?
- 3. Hypotheses
- tentative explanations of a phenomena phrased in such a way
as to be testable.
- 4. Predictions
- logical, testable outcomes of the hypotheses developed by
the use of deductive reasoning, eg. if .... (statement of hypotheses)
is true, then ... (predictions).
- 5. Tests
- determine if predictions are supported (fail to falsify).
- experimental tests differs from the control test by a single
factor, called the variable.
- a control is
a replica of the experiment in which the special treatment being
studied is omitted. Controls
clarify experimental results by establishing
a standard for comparison. Without a control, it is not possible
to say if experimental outcome is due to variable tested or
some other variable.
- The scientific process simply falsifies or supports hypotheses. Science
never proves anything. Hypotheses are never proven with absolute certainty,
only with a certain statistical degree of confidence. Gradually, as
repeated testing supports a particular hypotheses, we come to have greater
confidence in the hypotheses.
- Science is an adaptable process, not rigid. (eg, controls can not
always be used especially where experiments are done in nature).
- Science is tentative, it does not prove, only falsifies.
- Science requires critical thinking at every step.
- Cumullative (often observations are simply previous results).
- Self-critical: always open to revision by additional data. It is
a social activity with a self-correcting mechanism.
- Science itself is devoid of moral content. However, the knowledge
that we gain from applying scientific method to the uncovering of the
mysteries of nature does help humans decide what is "right"
or "wrong". Do not look to nature for a moral compass.
- Many questions lie outside the realm of science. There are limits
to science. Only deals with observable, quantifiable, testable phenomena
in the natural world. Not for use with the "supernatural".
Will not answer the question "Does God Exist?"
- "Freedom in science is essential." Is it?
Biology is connected to our lives
in many ways
- Some of the biggest challenges facing humanity have biological underpinnings.
A basic understanding of biology is necessary for an informed position
on many issues.
- Some of these issues include: human population growth, climate change, pollution, endangered species, genetic engineering, nutrition, medical advances, disease, etc...
- Biology- from molecular to ecosystem levels- is directly connected
to our lives.
- Evaluating reports on problems of this magnitude requires critical
thinking and familiarity with many aspects of biology (politicians and
lawers should be biologically literate).
- Biology offers us a deeper understanding of ourselves and the planet.
- Practical implications of biology: Technology
= application of scientific knowledge.
- Potent combination of science and technology has had profound effects
on society. Many effects have been beneficial. Others have inerdvertantly
been harmful (e.g. reduction of death rates through better health care
has led to human over population of earth, possibly beyond it's carrying
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