Transcript Overview of Life`s Unity

Invitation to Biology
Organization Within An Organism
 Atoms are organized into molecules
 In multicelled species, cells are organized into
tissues, organs, and organ systems
 All organisms consist of one or more cells
Organization of Groups of Organisms
 Population
• All individuals of one species in a specific area
 Community
• All populations in a specific area
 Ecosystem
• A community interacting with its environment
Organization of Life on Earth
 Biosphere
• All regions of Earth that hold life
• Land, water, and atmosphere
Levels of Organization
Levels of Organization
Overview of Life’s Unity
 Organisms require energy and materials to
sustain their organization and activities
• Nutrients are required for growth and survival
• Producers make their own food
• Consumers eat other organisms
Ecosystem:
Energy Flow and Material Cycling
Overview of Life’s Unity
 Organisms sense change
• Receptors respond to stimulation
• Responses keep internal conditions within ranges
that cells can tolerate (homeostasis)
Overview of Life’s Unity
 Organisms grow and reproduce
• Based on information encoded in DNA
• Inheritance transmits DNA from parents to
offspring through reproduction mechanisms
• Development transforms first cell into an adult
KEY CONCEPTS:
LIFE’S UNDERLYING UNITY
 All organisms are alike in key respects:
• Consist of one or more cells
• Live through inputs of energy and raw materials
• Sense and respond to changes in their external
and internal environments
• Cells contain DNA (molecule that offspring inherit
from parents; encodes information necessary for
growth, survival, and reproduction)
So Much Unity, So Many Species
 The world of life, past and present, shows great
diversity
 Classification systems organize species in ever
more inclusive groups
Genus and Species
 Species: One kind of organism
 Each species has a two-part name
• First part: Genus name
• Combined with the second part, it designates one
particular species
Domains
 Current classification groups all species into
three domains
• Bacteria (single-celled prokaryotes)
• Archaea (single-celled prokaryotes)
• Eukarya (protists, plants, fungi, and animals)
Bacteria and Archaea
Bacteria
Archaea
Eukarya
Eukarya
Eukarya
Eukarya
An Evolutionary View of Diversity
 Life’s diversity arises from mutations
• Changes in molecules of DNA which offspring
inherit from their parents
 In natural populations, mutations introduce
variation in heritable traits among individuals
Variation in Heritable Traits
 Some trait forms are more adaptive than others
• Bearers are more likely to survive and reproduce
 Over generations, adaptive forms of traits tend
to become more common in a population
• Less adaptive forms of the same traits become
less common or are lost
Evolution
 Populations evolve
• Traits that help characterize a population (and a
species) can change over generations
 Evolution
• Change which occurs in a line of descent
Selection
 Natural selection
• In natural populations
• Differential survival and reproduction among
individuals that vary in one or more heritable traits
 Artificial selection
• Breeding of captive populations
• Traits selected are not necessarily adaptive
Artificial and Natural Selection
Critical Thinking and Science
 Critical thinking is a self-directed act of judging
the quality of information as one learns
 Science is a way of looking at the natural world
• Helps minimize bias in judgments
• Focuses on testable ideas about observable
aspects of nature
How Science Works
 Researchers generally
• Observe something in nature
• Form hypotheses (testable assumptions) about it
• Make predictions about what might occur if the
hypothesis is not wrong
• Test their predictions by observations,
experiments, or both
Experiments
 Tests used to support or falsify a prediction
• Variable characteristic is measured and changed
• In the control group, variables do not change
A Scientific Approach
Hypothesis
Olestra® causes intestinal cramps.
Prediction
People who eat potato chips made with Olestra will be more
likely to get intestinal cramps than those who eat potato chips
made without Olestra.
Experiment
Results
Control Group
Experimental Group
Eats regular
potato chips
Eats Olestra
potato chips
93 of 529 people
get cramps later
(17.6%)
89 of 563 people
get cramps later
(15.8%)
Conclusion
Percentages are about equal. People who eat potato chips
made with Olestra are just as likely to get intestinal cramps
as those who eat potato chips made without Olestra.
These results do not support the hypothesis.