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

Life in the Trees The lives of gray-headed flying foxes are closely entwined with the lives of the eucalyptus trees that form their habitat Eucalyptus trees provide food and roosting sites for the flying foxes Flying foxes aid in eucalyptus pollination and help disperse the resulting seeds

Flying foxes are becoming an endangered species, partly because of habitat destruction

Biology is the scientific study of life THE SCOPE OF BIOLOGY Biology is the scientific study of life Interactions between different kinds of organisms affect the lives of all Recall the example of flying foxes and eucalyptus trees

Big Themes throughout the year Organization Hierarchy Structure and Function Evolution

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  organelles 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 * Based on observations and measurements Figure 1.2

In hypothesis-driven science, scientists use the “scientific method” They propose a hypothesis They make deductions leading to predictions They then test the hypothesis by seeing if the predictions come true

http://www.youtube.com/watch?v=jPaGOHwv7mQ

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

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 What do we do and what are possible outcomes? Discuss with partner Figure 1.3B

Experiments designed to test hypotheses must be controlled experiments Control groups must be tested along with experimental groups for the meaning of the results to be clear Controls provide comparison and must be repeatable A good hypothesis is testable and falsifiable

Variables Independent variable – factor manipulated in experiment Dependent variable – factor being measured that is predicted to be affected by independent variable.

Case study: spider mimicry Figure 1.3C So what do you notice between the spider and the fly? Explain the graph to the right. 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 Grouping organisms by fundamental features helps make the vast diversity of life manageable for study Scientists classify organisms into a hierarchy of broader and broader groups

Most classification schemes group organisms into three domains: Domain Bacteria common E.coli/Staph Domain Archaea Extreme hot/salt Figure 1.4A, B

Domain Eukarya Figure 1.4C-F

Know basic characteristics of each Domain as well as the eukaryotic Kingdoms. Plants Fungi Animalia Protists

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 These orchids show the variety possible within one species Figure 1.5A

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

DNA is universal – all life uses 4 bases. A particular sequence of nucleotides means the same thing even if in different organisms. Protein hemoglobin binds oxygen but can track evolutionary changes in DNA for hemoglobin Differences between organisms is due to differences in sequence (order) vs. code Similarities potentially show evolutionary trends.

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

Species change over time as they accumulate changes due to different environments – descent with modification. Natural selection is due to descent with modification

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

With your group Pick an organism and then decide which adaptations make it uniquely suitable for where it is found. Why these adaptations for this environment? Is there a better way, or what might happen in the future?

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

Darwin observations   Individuals vary in their traits (many passed from parent to offspring).   Organisms seem to produce more offspring than the environment can support.   Species suited to environment Organisms are not created but constantly edited to fit

Evolutionary tree

Think about it - question Explain why editing is an appropriate metaphor for how natural selection acts on a population’s heritable variation.

Think about it – possible answer Those with traits better suited to environment are more likely to reproduce. Those offspring better suited then other offspring and have advantage (until environment changes)

1.7 Living organisms and their environments form interconnecting webs The theory of natural selection applies to all levels in life’s hierarchy In an ecosystem, these interactions make up a complex web of relationships The functional aspects of an ecosystem come from the structure of the ecosystem’s web This is an interaction of living and non-living components.

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 Matter gets recycled 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

Many technological advances stem from the scientific study of life Evaluating everyday reports in the press about a large range of subjects requires critical thinking and some familiarity with many areas of biology In order to understand how rain forest destruction impacts global climate, it is important to understand biology from the molecular to the ecosystem level Figure 1.8B