Invitation to Biology

Chapter 1

Life’s Levels of Organization

• The world of life shows levels of organization, from the simple to the complex, which extend through:– cells– populations– communities– ecosystems– the biosphere

Molecules of Life• All things are made up of the same units of

matter: – atoms, molecules

• Living things are made of up of a certain subset of molecules:– nucleic acids, proteins, carbohydrates, lipids

DNA (deoxyribonucleic acid)

• The signature

molecule of life

• Molecule of

inheritance

• Directs assembly

of amino acids

Heritability of DNA

Inheritance– Acquisition of traits by way of

transmission of DNA from parent to offspring

Reproduction – Mechanisms by which an organism

produces offspring – Governed by instructions in DNA

DNA Guides Development

Development

– Transformation from fertilized egg to adult

– Series of stages

– Instructions for each stage in DNA

Energy Is the Basis of Metabolism

Energy = Capacity to do work

Metabolism = Reactions by which cells acquire and use energy to

grow, survive, and reproduce

Interdependencies among Organisms

ProducersMake their own food

ConsumersDepend on energy stored in

tissues of producers

DecomposersBreak down remains and wastes

Energy Flow

• Usually starts with energy from sun

• Transfer from one organism to another

• Energy flows in one direction• Eventually, all energy flows

back to the environment

energy input (mainly sunlight)

producers(plants and other self-feeding organisms;

they make their own food from simple raw materials)

nutrientcycling

consumers, decomposers(animals, most fungi, many protists,

many bacteria that can’t make their own food)

energy output (mainly metabolic heat)

Sensing and Responding

• Organisms sense changes in their environment and make responses to them

• Receptors detect specific forms of energy

• The form of energy detected by a receptor is a stimulus

Homeostasis

• Maintenance of internal environment within range suitable for cell activities

• Pancreas maintains level of sugar in blood by secreting hormones

Unity of Life

All organisms:

– Are composed of the same substances

– Engage in metabolism

– Sense and respond to the environment

– Have the capacity to reproduce based

on instructions in DNA

Diversity of Life

• Millions of living species

• Additional millions of species now

extinct

• Classification scheme attempts to

organize this diversity

Scientific Names

• Two-part naming system devised by

Carolus Linnaeus

• First name is genus (plural, genera)

– Homo sapiens - genus is Homo

• Second name is species within genus

• Bacteria

• Archaea

• Eukarya (includes protists, plants, fungi,

and animals)

Three-Domain Classification

Bacteria(EUBACTERIA)

Archaea(ARCHAEBACTERIA)

Eukarya(EUKARYOTES)

Life’s Diversity

Prokaryotes

Archaea and Bacteria

• Single-celled

• No nucleus or organelles

• Include producers, consumers,

decomposers

Eukaryotes

Eukarya (plants, fungi, animals, protists)

• DNA is inside a nucleus

• Most are larger and more complex than the prokaryotes

Plants

• All are multicelled

• Most are photosynthetic

producers

• Make up the food base for

communities, especially on

land

Fungi

• Most are multicelled

• Consumers and decomposers

• Extracellular digestion and

absorption

Animals

• Multicelled consumers– Herbivores

– Carnivores

– Parasites

– Scavengers

• Move about during at least some stage of their life

Mutation: Source of Variation

• Mutation = change in structure of DNA

• Basis for the variation in heritable traits

• Most are harmful

Adaptive Trait

A trait that gives the individual an advantage in survival or reproduction,

under a given set of circumstances

Evolution

• Genetically based change in a line of descent over time

• Population changes, not individuals

Natural Selection

• The outcome of differences in survival and reproduction among individuals that vary in details of heritable traits

• This process helps explain evolution - changes in a line of descent over generations

Artificial Selection

• Breeders favor some form of traits over others

• Individuals exhibiting favored traits are bred

• Favored traits increase in the population

Observations, Hypotheses, and Tests

• Observe phenomenon

• Develop hypotheses

• Make predictions

• Devise test of predictions

• Carry out test and analyze results

Scientific Theory

• A hypothesis that has been tested for its predictive power many times and has not yet been found incorrect

• Has wide-ranging explanatory power– Darwin’s Theory of Evolution by Natural

Selection

Role of Experiments

• Procedures used to study a phenomenon under known conditions

• Allows you to predict what will happen if a hypothesis is not wrong

• Can never prove a hypothesis 100% correct

Experimental Design

• Control group

– A standard for comparison

– Identical to experimental group except for

variable being studied

• Sampling error

– Non-representative sample skews results

– Minimize by using large samples

CONTROL GROUPGets regularpotato chips

EXPERIMENTAL GROUPGets Olestra potato chips

Make Prediction

Eat potato chips Eat potato chips

Analyze Results

Draw ConclusionEating Olestra potato chips

does not cause intestinal distress

If Olestra® potato chips cause intestinal distress then people who eat them will get cramps

Perform Experiment

93 of 529 people (17.6%)suffer from cramps later

89 of 563 people (15.8%)suffer from cramps later

About the same number of people in each group get cramps

Field Experiment

Control Group 34 H. cydnoindividuals

with yellow markings

Experimental Group

46 H. cydno individuals

with white markings

ExperimentBoth yellow and white formsof H. cydno butterflies areintroduced into isolatedrain forest habitat of yellowH. eleuchia butterflies.Numbers of individualsresighted recorded on adaily basis for two weeks.

ResultsExperimental group (H. cydno individuals without yellow wing markings) is selected against. 37 of the original group of 46white butterflies disappear (80%), compared with 20 of the 34 yellow controls (58%).

• Study of Heliconius butterflies

Limits of Science

• Scientific approach cannot provide answers to subjective questions

• Cannot provide moral, aesthetic, or philosophical standards

Science and the Supernatural

• Science has run up against religious

belief systems

– Copernicus suggested that sun, not the

Earth, was center of universe

– Darwin suggested that life was shaped by

evolution, not a single creation event

Asking Questions

• Scientists still ask questions that

challenge widely held beliefs

• The external world, not internal

conviction, is the testing ground for

scientific beliefs