Download Biology II – CHAPTER 1: An Introduction to Life on Earth

Biology II – CHAPTER 1: An Introduction to Life on Earth

What Are the 7 Characteristics of Living Things?
o Living things have a complex, organized structure that consists largely of organic molecules.
o Living things respond to stimuli from their environment.
o Living things actively maintain their complex structure and their internal environment, a process
called homeostasis.
o Living things acquire and use materials and energy from their environment and convert them
into different forms.
o Living things grow.
o Living things reproduce themselves, using a molecular blueprint called DNA.
o Living things, as a whole, have the capacity to evolve.
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Living things have a complex, organized structure that consists largely of organic molecules.
o Life is both complex and organized
o Have a precise arrangement
o Organized into specific combinations, structures, and systems
o Levels of organization of matter
 All life is built on the chemical foundation of substances called elements – each a unique
form of matter.
 The atom is the smallest unit of matter
 The cell is the smallest unit of life
 All cells contain genes – units of heredity that provide the information needed to
control the life of the cell

Living things Respond to Stimuli
o Organisms perceive and respond to stimuli in their internal and external environments.
o Internal stimuli are perceived by receptors for stretch, temperature, pain, and various chemicals.
o External responses to the internal stimuli are achieved by choosing the appropriate object or
movement
o External stimuli are perceived by receptors that trigger a response physically and/or chemically
 Offensive or defensive response depending on the stimulus

Living Things Maintain Relatively Constant Internal Conditions Through Homeostasis
o To stay alive and function effectively, organisms must keep the conditions within their bodies
fairly constant
o Homeostasis: the maintenance of a relatively constant environment required for the optimal
functioning of cells, maintained by the coordinated activity of numerous regulatory mechanisms,
including the respiratory, endocrine, circulatory, and excretory systems.
o Maintained by a variety of automatic mechanisms
 Temperature – sweating
 Hunger - eating
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Living Things Acquire and Use Materials and Energy
o Living things acquire and use materials and energy from their environment and convert them
into different forms.
o Organisms need materials and energy to maintain their high level of complexity and
organization, to grow, and to reproduce.
o Organisms acquire the atoms and molecules they need from air, water, or soil or from other
living things.
 These materials are called nutrients – extracted from the environment and incorporated
into the molecules of the organisms’ bodies
o The sum total of all of the chemical reactions needed to sustain an organism’s life is called its
metabolism.
o Organisms obtain energy – the ability to do work
 Occurs in one of two ways:
 Photosynthesis: capturing the energy of sunlight and store it in energy-rich sugar
molecules
 Consuming energy-rich molecules contained in the bodies of other organisms
o The energy that sustains nearly all life comes from sunlight – energy flows from the sun through
nearly all forms of life.
o Organisms that cannot photosynthesize depend on photosynthetic life-forms for food, either
directly or indirectly.
o Energy is eventually released again as heat.

Living Things Grow
o At some time in its life cycle, every organism becomes larger – it grows.
o Growth involves the conversion of materials acquired from the environment into the specific
molecules of the organism’s body.
o Growth is not a failure of Homeostasis
o Development occurs in stages from birth to death – genetically programmed parts of the
organism’s life cycle.
 Depending on the organism, depends on the number of growth stages it will go through
in its lifetime.

Living Things Reproduce
o Organisms reproduce, giving rise to offspring of the same type and creating continuity of life.
o The diversity of life occurs in part because offspring are usually somewhat different from their
parents
o The specific mechanisms by which traits are passed from one generation to the next, using
genetic information that is recombined in various ways
 The different genetic material provided by their parents creates genetic variability
o Reproduction is not a failure of Homeostasis.
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o Living things must reproduce to continue the existence of a species
 Asexually: one organism divides into two complete, independent organisms
 Sexually: two organisms combine genetic information to produce offspring with all
necessary genetic information to live
o DNA Is the Molecule of Heredity
 All known forms of life contain their hereditary information within a molecule called
DNA (deoxyribonucleic acid)
 The structure and function of this molecule are found in the segments of DNA called
genes.
 DNA is the genetic blueprint or molecular instruction manual.
 When an organism reproduces, it passes a copy of its DNA to its offspring.
 If an error occurs, called a mutation, it can produce variety within a species
ultimately giving way to evolution.

Living Things As a Whole Have the Capacity to Evolve
o Living things have the capacity to evolve, therefore, over time mutations and variable offspring
create diversity in the genetic material of a species or evolution.
o The scientific theory of evolution states that modern organisms descended – with modification –
from preexisting life-forms, ultimately sharing a common ancestor.
o The most important force of evolution is natural selection - the process by which organisms
with adaptations survive and reproduce more successfully than do others that lack those traits.
o Adaptations: characteristics that help an organism cope with the rigors/changes of its
environment
 Adaptive traits are passed on to the next generation so that survival is optimized.

How Do Scientists Categorize the Diversity of Life?
o Organisms can be grouped into 3 major categories or domains:
 Bacteria – single-celled, simple organisms
 Archaea – single-celled, simple organisms
 Eukarya – multicellular, highly complex organisms
o Domain classification reflects the fundamental differences among the cell types that compose
these organisms
o Eukarya domain is further classified into 3 major subdivisions or kingdoms:
 Fungi
 Plantae
 Animalia
o As well as a diverse collection known as “protists” that are mostly single-celled organisms
o Some Characteristics Used in Classification of Organisms
 2 types of cells:
 Prokaryotic – do not have a nucleus; genetic material resides in their cytoplasm
o The domains Bacteria and Archaea
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Eukaryotic – have a “true” membrane-enclosed nucleus; generally larger than
prokaryotes
o The domain Eukarya
2 types of organisms:
 Unicellular – single-cell organism; mainly live independently of other organisms
and able to survive on their own
 Multicellular – their lives depend on intimate communication and cooperation
among many specialized cells to survive
o Members of the Different Kingdoms Have Different Ways of Acquiring Energy
 Autotrophs or “self-feeders” make their own food and energy
 Photosynthetic organisms capture energy from sunlight and store it in molecules
such as sugars and fats
 Plants, some bacteria, some protests


Heterotrophs or “other-feeders” depend on others for food and energy
 Archaea, bacteria, protists, and all fungi and animals
 The size of food they eat differs among organisms

Absorb food molecules, Ingest food (eat whole chunks) or Digest food (breaking down
food into molecules)
What is the Science of Biology?
o The same principles and methods that are used in other sciences are used in Biology.
 The basic principle of modern biology is that living things obey the same laws of physics
and chemistry that govern nonliving matter.
o Scientific Principles Underlie All Scientific Inquiry
 All scientific inquiry is based on assumptions
 Must be thoroughly tested and validated, but can never be proven absolutely

3 Scientific Principles
 Natural Causality
o All events can be traced to natural causes that are potentially within our
ability to understand.
o The natural evidence we gather has not been deliberately distorted to fool
us – we have to trust the evidence given to us by nature, otherwise science
is useless.

Uniformity in Space and Time
o Natural laws are uniform in space and time and do not change with
distance or time
o Natural laws today are the same as they were millions of years ago
 Laws of gravity
 The behavior of light
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Common Perception
o All human beings general perceive natural events in the same way
o Value systems are commonly used
 Subjective not objective
 Science cannot use these to solve certain types of philosophical or
moral problems/questions
o The Scientific Method Is the Basis for Scientific Inquiry
 A rigorous method for making observations of specific phenomena and searching for the
order underlying those phenomena

4 Interrelated Operations:
 Observation – the beginning of all scientific inquiry
o Observe a phenomenon that provokes a question
 Hypothesis – a supposition or “educated guess”
o Provides a possible explanation for the observed phenomenon
o Must be able to be tested
 Experiment – controlled observations
o Produce results that either support or refute the hypothesis
 Conclusion – the decision made by on evidence that validates the hypothesis

A single experiment is never enough to support a conclusion – results must be repeated
by the original researcher and others


Variable – a single factor that is the cause of a single observation
Controls – factors that make sure all other variables are constant and do not interfere
with the experiment

The scientific method can be used not only to generate new knowledge, but to solve
everyday problems
There are limitations – seldom are all variables in control except the one being studied;
therefore, any experiment is subject to revision based on any new observations.
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
Communication is the final most important element – experiment details must be
communicated thoroughly and accurately so that it can be repeated and verified by
others.
o Scientific Theories have been Thoroughly Tested
 Scientific Theory – a general explanation of natural phenomena based on extensive and
repeated observable evidence
 If new compelling evidence arises within a theory, then it will be modified
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Inductive reasoning – the process of creating a generalization based on a result of many
observations that support the theory – cannot be contradicted
Deductive reasoning – the process of generating a hypothesis about how a specific
experiment will turn out – Usually stated as an “If…then” statement
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
Evolution: The Unifying Theory of Biology
o Evolution is the unifying theory that explains the origin of diverse forms of life as a result of
changes in their genetic makeup.
o Three Natural Processes that Underlie Evolution:
 Genetic Variation
 Variation occurs among members of a population
 Mainly influenced by genes
 Mutations sometimes improve an organism’s ability to survive and reproduce
 Inheritance
 Variations of offspring from parents who carry that variations
 Much of the variability among organisms is inherited
 Natural Selection
 The survival and enhanced reproduction of organisms with favorable variations
 Natural selection tends to preserve genes that help an organism to survive and
reproduce
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
Adaptations – structures, processes, or behaviors that aid in survival and
reproduction in a particular environment
o What helps an organism survive today can become a liability tomorrow
o The genetic makeup that best adapts an organism to its current
environment will eventually change over time
The diversity of species and the complex interrelationships with one another that sustains
life is called biodiversity.
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