121 ch1 introduction

transcript

Biology 121 – Concepts of BiologyDr. Fritzler

Chapter 1Chapter 1

Introduction: Biology Today

• We are living in a golden age of biology.

• Biology provides exciting breakthroughs changing our culture.

– Genetics and cell biology are revolutionizing medicine and agriculture

– Molecular biology is solving crimes and revealing ancestries.

– Ecology helps us address environmental issues.

– Neuroscience and evolutionary biology are reshaping psychology and sociology.

Biology and Society: Biology All Around Us

• Biology is the scientific study of life.

– How does “life” differ from “non-life”?

– Where does “life” start?

– What is “nature”?

The Properties of Life

1) Order – complex but ordered organization

2) Regulation – outside environment may change, but organism can regulate inner environment

- Homeostasis

The Seven Properties of Life

3) Growth & Development – DNA controls pattern of growth and development

- Every organism arises through reproduction- Inheritance transmits DNA

from parents to offspring

4) Energy Utilization – take in energy and use it to perform all of life’s activities

5) Response to the Environment – all organisms respond to environmental stimuli

6) Reproduction – organisms reproduce their own kind

7) Evolution – populations evolve (change) over time

- Evolution is the central, unifying feature of life since life arose nearly 4 billion years

Seahorse Camouflage

• Biologists explore life at levels ranging from the biosphere to the molecules that make up cells.

• “Life” emerges at the level of cells

– A cell is the smallest unit that can live and reproduce on its own (perform all properties of life)

– All organisms consist of one or more cells

• Life is more than a sum of its parts, it is an emergent property

Life at Its Many Levels

BiosphereEcosystems

Communities

Populations

BiosphereEcosystems

Communities

Populations

Organisms

Organ Systemsand Organs

Tissues

BiosphereEcosystems

Communities

Populations

Organisms

Organ Systemsand Organs

Tissues

Organelles

Molecules and AtomsAtom

Nucleus

Ecosystems• Each organism interacts continuously with living

and nonliving factors in its environment.

– The interactions between organisms and their environment take place within an ecosystem.

• The dynamics of any ecosystem depend on two main processes:

– Cycling of nutrients

– One-way flow of energy

Energy and Nutrients• All organisms require energy and nutrients to

sustain their organization and activities

– Nutrients – required for growth and survival

– Producers – make their own food; get energy from sun

– Consumers – obtain energy and nutrients by eating other organisms

– Decomposers – consumers (bacteria, fungi) that recycle complex molecules

Inflowof lightenergy

Chemicalenergyfood

Cyclingof

nutrients

Consumersanimals

Producersplants and otherphotosyntheticorganisms

Decomposersin soil

Loss ofheat

energy

ECOSYSTEM

- Nutrients are cycled

- One-way flow of energy

If So Much Unity, Why So Many Species?

• All organisms

– Made from same materials

– Function on same laws of energy

– Have same properties of life

• Diversity is the hallmark of life

– The diversity of known life includes 1.8 million species.

– Estimates of the total diversity range from 10 million to over 100 million species.

Grouping Species: The Basic Concept

• Biodiversity can be beautiful but overwhelming.

• Species – One kind of organism

• Two part name – Genus species

• Ex. Homo sapiens

The Three Domains of Life• The three domains of

life are:

– Bacteria – single-celled, prokaryotes (no nucleus), most ancient

– Archaea – single-celled, prokaryotes

– Eukarya – eukaryotes (with a nucleus), single- and multi-celled

• Eukarya includes

– Kingdom Plantae

– Kingdom Fungi

DOMAIN EUKARYA

Kingdom Plantae Kingdom Fungi

Kingdom Animalia Protists multiple kingdoms

– Kingdom Animalia

– Protists (single-celled)

Unity in the Diversity of Life• How can organisms be so much alike and still

show tremendous diversity?

• Underlying the diversity of life is a striking unity, especially at the lower levels of structure.

– For example, all life uses the genetic language of DNA.

– Changes in DNA (mutations) which are inherited from parents give rise to diversity

• Biological evolution accounts for this combination of unity and diversity.

EVOLUTION: BIOLOGY’S UNIFYING THEME• Mutations give rise to different forms of traits

• Some trait forms are more adaptive than others

– Those that have them are more likely to survive and reproduce in their environment

• Over generations, adaptive forms of traits tend to become common in a population

– Less adaptive forms of the same traits become less common or lost

Evolution• Evolution is heritable change which occurs in a

line of descent over time

• Populations evolve…not individuals!

– Traits that help characterize a population (and a species) can change over generations

– Each species is one twig of a branching tree of life extending back over 3 billion years.

– Species that are very similar, such as brown bears and polar bears, share a more recent common ancestor.

Ancestralbear

Common ancestor ofpolar bear and brown bear

Giant panda

Spectacled bear

Sloth bear

Sun bear

American black bear

Asiatic black bear

Polar bear

Brown bear

30 25 20 15 10 5

Millions of years ago

Evolution via Selection• Natural Selection

– Natural populations– Differential survival and

reproduction among individuals that vary in one or more heritable traits

• Artificial Selection– Captive populations– Traits selected are not

necessarily adaptive

rock pigeon

Observing Natural Selection

Population with varied inherited traits

Elimination of individuals with certain traits

Observing Natural Selection

Reproduction of survivors

Increasing frequency of traits that enhancesurvival and reproductive success

Reproduction of survivors

Observing Artificial Selection

Domesticated dogs descended from wolves

Domesticated dogs Gray wolves

THE PROCESS OF SCIENCE• The word science is derived from a Latin verb

meaning “to know.”

– Science is a way of looking at the natural world

– Minimize bias in judgments

– Focus on testable ideas about observable aspects of nature

Scope and Limits of Science• Limit science to only that which is observable in

nature

– Allows us to be objective, not subjective

• Science does not address the supernatural or anything beyond nature

How Science Works• The Scientific Method

– Observe something in nature

– Form hypothesis (testable assumption) about it

– Make predictions about what might occur of the hypothesis is not wrong

– Test predictions by observations or experiments

– Repeat for consistency

– Report tests and conclusions

Experiments• Tests used to support or falsify a prediction

– Variable group – characteristic is measured and changed

– Control group – characteristics do not change

• Experiments focus on cause, effect, or function of one variable at a time

– Minimizes bias and controls potential bias in results

Observation:My flashlightdoesn’t work.

Question:What’s wrong

with myflashlight?

Hypothesis:The flashlight’s

batteriesare dead.

Prediction:If I replace thebatteries, theflashlight will

with myflashlight?

Experiment:I replace the

batteries withnew ones.

Experimentsupports

hypothesis;make additional

predictionsand test them.

batteriesare dead.

with myflashlight?

Experiment:I replace the

batteries withnew ones.

Experimentsupports

hypothesis;make additional

predictionsand test them.

Experiment doesnot support

hypothesis; revisehypothesis orpose new one.

Revise

batteriesare dead.

HypothesisOlestra® causes intestinal cramps.

PredictionPeople who eat potato chips made with Olestra will be morelikely to get intestinal cramps than those who eat potato chipsmade without Olestra.

Experiment Control Group Experimental Group

Percentages are about equal. People who eat potato chipsmade with Olestra are just as likely to get intestinal crampsas those who eat potato chips made without Olestra.These results do not support the hypothesis.

Conclusion

Eats regularpotato chips

Eats Olestrapotato chips

93 of 529 peopleget cramps later(17.6%)

89 of 563 peopleget cramps later(15.8%)

Results

Sampling Error in Experiments• Small sample size increases the likelihood of

sampling error in experiments

• In such cases, a subset may be tested that is not representative of the whole

• Larger sample size and repetition can reduce sampling error

30% green

70% black

Out of 50:

10 (20%) green, 40 (80%) black

Theories in Science• What is a scientific theory, and how is it different from a

hypothesis?

– A theory is a set of well-tested hypotheses that explain some aspect of the natural world

– Explains a broad range of observations (each hypothesis is narrow)

– NOT the absolute truth; can only be relatively certain that it is or is not correct (ex: gravity)

– Opinion and belief are NOT scientific theory

– Science and religion are two very different ways of trying to make sense of nature

Evolution Connection:Evolution in Our Everyday Lives• Antibiotics are drugs that help fight bacterial

infections.

• When an antibiotic is taken, most bacteria are typically killed.

• Those bacteria most naturally resistant to the drug can still survive.

• Those few resistant bacteria can soon multiply and become the norm and not the exception.

• The evolution of antibiotic-resistant bacteria is a huge problem in public health.

• Antibiotics are being used more selectively.

• Many farmers are reducing the use of antibiotics in animal feed.

121 ch1 introduction

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