Invitation to Biology

Chapter 1

1.1 Impacts/Issues:The Secret Life of Earth

Biology • The systematic study of life

We have encountered only a fraction of the organisms that live on Earth• Scientists constantly discover new species• Extinction rates are accelerating

Video: Lost worlds and other wonders

Exploring New Guinea

A rare golden-mantled tree kangaroo

1.2 Life’s Levels of Organization

The building blocks (atoms) that make up all living things are the same ones that make up all nonliving things

The unique properties of life emerge as certain kinds of molecules become organized into cells

Life’s Levels of Organization

Atom• Fundamental building block of all matter

Molecule• An association of two or more atoms

Cell• Smallest unit of life

Organism• An individual; consists of one or more cells

Life’s Levels of Organization

Population• Group of individuals of a species in a given area

Community• All populations of all species in a given area

Ecosystem• A community interacting with its environment

Biosphere• All regions of Earth that hold life

Nature and Life

Nature• Everything in the universe, except what humans

have manufactured

Emergent property• A characteristic of a system that does not appear

in any of a system’s component parts

Levels of Organization in Nature

3

Fig. 1-2, p. 5

2

8

17

6

45

Animation: Life’s levels of organization

Active Figure: Levels of organization

1.3 Overview of Life’s Unity

All living things have similar characteristics• Require energy and nutrients• Sense and respond to change• Reproduce with the help of DNA

Energy Sustains Life’s Organization

One-way flow of energy through the biosphere and cycling of nutrients among organisms sustain life’s organization

Energy• The capacity to do work

Nutrient• Substance that is necessary for survival, but that

an organism can’t make for itself

Organisms and Energy Sources

Producers• Organisms that make their own food using

energy and simple raw materials from the environment

• Example: plants

Consumers• Organisms that get energy and carbon by feeding

on tissues, wastes, or remains of other organisms• Example: animals

Energy Flow and Material Cycling

Fig. 1-3a, p. 6

Fig. 1-3a, p. 6

sunlight energy A Producers harvest energy

from the environment. Some of that energy flows from producers to consumers.

PRODUCERSplants and other

self-feeding organisms

B Nutrients that become incorporated

into the cells of producers and consumers are

eventually released by decomposition. Some

cycle back to producers.

CONSUMERSanimals, most fungi,

many protists, bacteria

C All energy that enters the world of life eventually flows out of it, mainly as heat.

Fig. 1-3a, p. 6

sunlight energy A Producers harvest energy

from the environment. Some of that energy flows from producers to consumers.

PRODUCERSplants and other

self-feeding organisms

CONSUMERSanimals, most fungi,

many protists, bacteria

C All energy that enters the world of life eventually flows out of it, mainly as heat. Stepped Art

B Nutrients that become incorporated

into the cells of producers and consumers are

eventually released by decomposition. Some

cycle back to producers.

Fig. 1-3b, p. 6

Animation: One-way energy flow and materials cycling

Organisms Sense and Respond to Change

Organisms sense and respond to change to keep conditions in their internal environment within a range that favors cell survival (homeostasis)

Homeostasis• Set of processes by which an organism keeps its

internal conditions within tolerable ranges

Receptor• Molecule or structure that responds to a stimulus

Response to Stimuli

Organisms Grow, Develop and Reproduce

Organisms grow, develop, and reproduce based on information encoded in DNA, which they inherit from their parents

Growth• Increase in size, volume, and number of cells in

multicelled species

Development• Multistep process by which the first cell of a new

individual becomes a multicelled adult

Organisms Grow, Develop and Reproduce

Reproduction• Process by which parents produce offspring

Inheritance• Transmission of DNA from parents to offspring

DNA (Deoxyribonucleic acid)• Molecule that carries hereditary information about

traits

1.4 Introduction to Life’s Diversity

The millions of species on Earth vary greatly in details of body form and function

Each species is given a unique two-part name that includes genus and species names

Species• A type of organism

Genus• Group of species that share a unique set of traits

Classification Systems

Classification systems group species according to traits and organize information about species

One system sorts all organisms into one of three domains: Bacteria, Archaea, and Eukarya

The eukaryotes include plants, protists, fungi and animals

Life’s Diversity: Three-Domain Classification System

Fig. 1-5, p. 8

Bacteria Archaea

Eukarya

Animation: Life’s diversity

Prokaryotes

Prokaryotes• Single celled organisms in which DNA is not

contained in a nucleus

Bacterium• A member of the prokaryotic domain Bacteria

Archaeans• A member of the prokaryotic domain Archaea

Eukaryotes

Eukaryotes• Organisms whose cells typically have a nucleus

Fungus• Eukaryotic consumer that obtains nutrients by

digestion and absorption outside the body

Protists• Eukaryotes that are not plants, animals, or fungi

Eukaryotes

Plant• Typically a multicelled, photosynthetic producer

Animal• Multicelled consumer that develops through a

series of embryonic stages and moves about during all or part of the life cycle

Animation: Three domains

1.5 The Nature of Scientific Inquiry

Critical thinking• Mental process of judging the quality of information

before deciding whether or not to accept it

The Scope and Limits of Science

Science is a way of looking at the natural world which helps us to communicate our experiences without bias by focusing only on testable ideas about observable phenomena• Science does not address the supernatural

Science• The systemic study of nature

1.6 How Science Works

Researchers make and test potentially falsifiable predictions about how the natural world works

Generally, scientific inquiry involves forming a hypothesis (testable assumption) about an observation then making and testing predictions based on the hypothesis

A hypothesis that is not consistent with the results of scientific tests is modified or discarded

Common Research Practices

1. Observe some aspect of nature

2. Frame a question about your observation

3. Propose a hypothesis (a testable explanation of the observation)

Common Research Practices

4. Make a prediction – a statement based on a hypothesis, about some condition that should exist if the hypothesis is not wrong

5. Test the accuracy of the prediction by experiments or gathering information (tests may be performed on a model)

Common Research Practices

6. Assess the results of the tests (data) to see if they support or disprove the hypothesis

7. Conclusions: Report all steps of your work and conclusions to the scientific community

Making Observations: A Field Study

A Scientific Theory

Scientific theory• A hypothesis that has not been disproven after

many years of rigorous testing• Useful for making predictions about other

phenomena

Laws of Nature

Law of nature• Generalization that describes a consistent and

universal natural phenomenon for which we do not yet have a complete scientific information

• Example: gravity

Examples of Scientific Theories

Animation: An example of the scientific method

1.7 The Power of Experiments

Natural processes are often influenced by many interacting variables

Variable• A characteristic or event that differs among

individuals

The Power of Experiments

Experiments simplify interpretations of complex biological systems by focusing on the effect of one variable at a time

Experiment• A test to support or falsify a prediction

Experimental and Control Groups

Experimental group• A group of objects or individuals that display or

are exposed to a variable under investigation

Control group• A group of objects or individuals that is identical

to an experimental group except for one variable

Potato Chips and Stomachaches

Fig. 1-7, p. 12

AOlestra® causes intestinal cramps.Hypothesis

B PredictionPeople who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra.

C Experiment Control Group Experimental Group

Eats regular potato chips

Eats Olestra potato chips

D 93 of 529 people get cramps later (17.6%)

89 of 563 people get cramps later (15.8%)

Results

E ConclusionPercentages 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.

Results 93 of 529 people get cramps later (17.6%)

89 of 563 people get cramps later(15.8%)

Experiment Control GroupEats regularpotato chips

Experimental GroupEats Olestrapotato chips

HypothesisOlestra® causes intestinal cramps.

PredictionPeople who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra

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.

Fig. 1-10, p. 14

Stepped Art

Example: Butterflies and Birds

Question• Why does a peacock butterfly flick its wings?

Two hypotheses• Exposing wing spots scares off predators• Wing sounds scare off predators

Two predictions• Individuals without spots are eaten more often• Individuals without sounds are eaten more often

Peacock Butterfly Defenses

Experiments and Results

Four groups of butterflies were exposed to predators (birds)• Butterflies without spots• Butterflies without sounds• Butterflies without spots or sounds• Control group

Test results support both original hypotheses

Results: Peacock Butterfly Experiment

Sampling Error

Biology researchers experiment on subsets of a group, which may result in sampling error

Sampling error• Difference between results derived from testing

an entire group of events or individuals, and results derived from testing a subset of the group

Sampling Error

Fig. 1-9, p. 14

24

20

16

12

8

Win

g-f

lick

s p

er m

inu

te

4

0– spots + sound

– spots – sound

+ spots – sound

Probability

Researchers try to design experiments carefully in order to minimize sampling error

Statistically significant• Refers to a result that is statistically unlikely to

have occurred by chance

Animation: Sampling error

1.8 Impacts/Issues Revisited

Biologists constantly discover new species• Mouse lemur (Microcebus lehilahytsara),

discovered in Madagascar in 2005

Digging Into Data:Peacock Butterfly Predator Defenses