CHAPTER 1 Introduction: The Scientific Study of Life Modules 1.1 – 1.3

THE SCOPE OF BIOLOGY Biology is the scientific study of life Interactions between different kinds of organisms affect the lives of all

1.1 Life’s levels of organization define the scope of biology A structural hierarchy of life, from molecules to ecosystems, defines the scope of biology An ecosystem consists of: all organisms living in a particular area all nonliving physical components of the environment that affect the organisms (soil, water)

At the top of life’s hierarchy is the ecosystem ECOSYSTEM LEVEL Eucalyptus forest Ecosystems include: all the organisms in an area, which make up a community interbreeding organisms of the same species, a population COMMUNITY LEVEL All organisms in eucalyptus forest POPULATION LEVEL Group of flying foxes ORGANISM LEVEL Flying fox Brain Spinal cord ORGAN SYSTEM LEVEL Nervous system ORGAN LEVEL Brain Nerve TISSUE LEVEL Nervous tissue CELLULAR LEVEL Nerve cell MOLECULAR LEVEL Molecule of DNA Figure 1.1

Organisms are made up of: organ systems organs tissues cells molecules ECOSYSTEM LEVEL Eucalyptus forest COMMUNITY LEVEL All organisms in eucalyptus forest POPULATION LEVEL Group of flying foxes ORGANISM LEVEL Flying fox Brain Spinal cord ORGAN SYSTEM LEVEL Nervous system ORGAN LEVEL Brain Nerve TISSUE LEVEL Nervous tissue CELLULAR LEVEL Nerve cell MOLECULAR LEVEL Molecule of DNA Figure 1.1

1.2 Scientists use two main approaches to learn about nature THE PROCESS OF SCIENCE 1.2 Scientists use two main approaches to learn about nature In discovery science, scientists describe some aspect of the world and use inductive reasoning to draw general conclusions Example: scientists have described how newborn flying foxes cling to their mother’s chest for the first weeks of life Figure 1.2

In hypothesis-driven science, scientists use the “scientific method”

1.3 With the scientific method, we pose and test hypotheses Observation The main steps of the scientific method Question Hypothesis Prediction Test does not support hypothesis; revise hypothesis or pose new one Test supports hypothesis; make additional predictions and test them Test: Experiment or additional observation Figure 1.3A

Observation Skills Observe the following scene quietly for 30 seconds.

Are there cars parked on the sides of the road? What color is the pickup truck driving in the road? Any minivans around? What does the blue sign say? What's the speed limit? Are there any pedestrians on the road?

Eye Witness 1 witness, 1 investigator

Deductive reasoning is used in testing hypotheses If a hypothesis is correct, and we test it, then we can expect a particular outcome Case study: flashlight failure Figure 1.3B

Experiments designed to test hypotheses must be controlled experiments Control groups must be tested along with experimental groups for comparison

Case study: spider mimicry Figure 1.3C Pounce rate (% of trials in which spider jumped on fly) Control group (untreated flies) Experimental group (wing markings masked) Figure 1.3D

Another test of the spider mimic hypothesis: wing transplants Number of stalk and attack responses by spiders Wing markings Wing waving Normal spider mimic Mimic with mimic wing transplant Mimic with housefly wing transplant Housefly with mimic wing transplant Normal housefly Figure 1.3E Controls Experimentals

1.4 The diversity of life can be arranged into three domains EVOLUTION, UNITY, AND DIVERSITY 1.4 The diversity of life can be arranged into three domains

order of taxa in biology (Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species) Dear King Philip Come Over For Good Soup

Most classification schemes group organisms into three domains: Domain Bacteria No nucleus 1 chromosome Domain Archaea Figure 1.4A, B

Domain Eukarya - cells have a membrane bound nucleus and organelles Figure 1.4C-F

1.5 Unity in diversity: All forms of life have common features All organisms share a set of common features, signs of unity in life’s vast diversity All are made of cells All have DNA as their genetic blueprint Figure 1.5A

DNA is made of chemical units called nucleotides Each species has its own nucleotide sequence Figure 1.5B

The genetic information in DNA underlies all of the features that distinguish life from nonlife Order and regulation Growth and development Use of energy from the environment Response to environmental stimuli Ability to reproduce Evolutionary change

1.6 Evolution explains the unity and diversity of life Charles Darwin is a central figure in biology He synthesized the theory of evolution by natural selection A theory in science is a comprehensive idea with broad explanatory power Evolution is the core theme of biology Figure 1.6A

The theory of natural selection explains the main mechanism whereby all species of organisms change, or evolve (1) Population with varied inherited traits (2) Elimination of individuals with certain traits Figure 1.6B (3) Reproduction of survivors

Evolution happens when populations of organisms with inherited variations are exposed to environmental factors that favor the success of some individuals over others Natural selection is the editing mechanism Evolution is based on adaptations Figure 1.6C

1.7 Living organisms and their environments form interconnecting webs The theory of natural selection applies to all levels in life’s hierarchy Video: #75 (natural selection CCR) http://www.youtube.com/watch?v=aTftyFboC_M In an ecosystem, these interactions make up a complex web of relationships

A web of interactions in a rain forest ecosystem Figure 1.7A

Plants, or plant products, are the ultimate sources of food in an ecosystem This African sunbird is consuming nectar, a plant product Figure 1.7B

Cycling of chemical nutrients Chemical nutrients cycle within an ecosystem’s web Energy flows in and out constantly Sun Inflow of light energy Loss of heat energy Air Chemical energy Cycling of chemical nutrients Organisms Soil Figure 1.7C ECOSYSTEM

1.8 Connection: Biology is connected to our lives in many ways BIOLOGY AND EVERYDAY LIFE 1.8 Connection: Biology is connected to our lives in many ways Biology is connected to a great number of important issues Environmental problems and solutions Genetic engineering Medicine Figure 1.8A

Process of Science (1.3)

Observation A farmer notices that his neighbors wheat yields are consistently higher than his own.

Testable Question What causes the other farmers fields to produce more grain?

Possibilities Farming Practices Variety of Seed Time of planting Summer fallow Fertilizing Pesticides

Outside Factors Less moisture due to varying weather patterns Poor Soil Other Neighbors fields holding pests

Hypothesis The farmer thinks that it is most likely the result of the seed variety.

Prediction If the farmer plants the same seed variety as his more successful neighbor, then his yields will be higher than with the old variety.

Controlled Experiment Independent Variable – The variable that will be changed by the conductor of the experiment. The variety of wheat seed

Controlled Experiment Dependent Variable – The variable that will be measured to determine the effect of the Independent Variable. The wheat yield

Controlled Experiment Controlled Variables – The variables that may have an effect on the dependent variable, but are not being tested, so must remain the same. Fertilizer, time of planting, seeding rate, moisture, weather damage, etc.

Controlled Experiment Controlled Variables – The variables that will not be allowed to change. Any measured difference will be due to the effect of the Independent Variable. Fertilizer, Pesticide, Time of Planting, Weather

Controlled Experiment Experimental Group- the group in which the Independent variable is changed. Control Group- group in which the independent variable is left unchanged. Controls other possible variables, used for comparison.

Controlled Experiment The farmer 10 separate strips and alternately plants 5 strips to his old variety and 5 to the new variety. The field is treated exactly the same for each variety.

Field

Results The farmer carefully harvests one variety and then the other. The new variety yields a total of 2,017 bushels, while his old variety yields 2,156 bushels.

Conclusions The farmer decides that the seed variety is not the factor that causes his neighbors yields to be higher.

Start Over The farmer thinks the next most likely variable is fertilizer. He repeats his experiment, this time using only one seed variety, while fertilizing one set of strips and not fertilizing the other.

Results The fertilized strips yield 2,562 bushels. The unfertilized strips yield 1,985 bushels.

Conclusions The farmer decides that the fertilizer made a drastic difference in yield and then compared the cost of the fertilizer with the yield increase. He then fertilized all of his cropland before planting.

(1.6) Evolution explains the Unity and Diversity of Life

Sexual Selection Gene Indicators Preferential Mating Individuals with “Good Gene” indicators are selected more for mating and pass on more genes to the next generation.

Common Characteristics of Living Things Order – complex organization (cells) Regulation – maintain internal environment (Homeostasis) Growth and Development Utilize Energy Respond to the environment Reproduction Evolution