Biology: Themes in the Study of Life Chapter 1

Life’s levels of organization define the scope of biology Emergent properties Life emerges at the level of the ________

Cells are the Structural and Functional Units of Life Two distinct groups of cells exist Prokaryotic cells lack membrane bound organelles simple and small, range in size from 1-10 µm ex. bacteria Eukaryotic cells Have membrane bound organelles; Can be a single cell, most are multicellular; 10-100 µm ex’s. plants, animals, fungi and protists

Prokaryotic cell Eukaryotic cell DNA (no nucleus) Membrane Nucleus (contains DNA) Organelles

Cells are the Structural and Functional Units of Life Form generally fits function By studying a biological structure, you can determine what it does and how it works.

Living Organisms Interact with their Environments To be successful, an ecosystem must recycle chemicals necessary for life & move energy through the ecosystem Biotic and Abiotic components must interact to accomplish this Biotic components Producers :Photosynthetic organisms that provide food for a typical ecosystem Consumers: Eat plants (or animals that profit from plants) Abiotic components Chemicals & nutrients required for life Ex’s. O2, CO2, water, visible light, etc.

Producers Consumers Ecosystem Sunlight Cycling of chemical nutrients Heat Chemical energy Consumers Figure 1.2 The cycling of nutrients and flow of energy in an ecosystem. Heat

EVOLUTION, THE CORE THEME OF BIOLOGY

The Unity of Life: All forms of life Have Common Features DNA is the genetic (hereditary) material of all cells A gene is a discrete unit of DNA Diversity of life results from differences in the sequence of chemical bases in DNA The chemical structure of DNA accounts for its function

Diversity Results from Differences in DNA Sequence

The Unity of Life All living things share common properties Order Regulation Growth and development Energy processing Response to the environment Reproduction Evolutionary adaptation

(3) Growth and development (4) Energy processing (1) Order (2) Regulation (3) Growth and development (4) Energy processing Figure 1.4B Some important properties of life. (5) Response to the environment (6) Reproduction (7) Evolutionary adaptation

The Diversity of Life Can be Arranged Into Three Large Domains Domain Bacteria—prokaryotic, mostly unicellular, microscopic Domain Archaea—prokaryotic, mostly unicellular, microscopic oldest and most extreme Domain Eukarya—eukaryotic cells, uni/multicellular with membrane bound organelles

Domain Eukarya Includes Four Kingdoms: K. Animalia, K. Plantae, K Domain Eukarya Includes Four Kingdoms: K. Animalia, K. Plantae, K. Fungi, K. Protista K. Protista K. Plantae K. Fungi K. Animalia

Evolution Explains the Unity and Diversity of Life In 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection The book accomplished two things Presented evidence to support evolution Proposed that the mechanism for evolution is natural selection

Evolution Explains the Unity and Diversity of Life Natural selection was inferred by connecting two observations Individuals within a population inherit different characteristics and vary from other individuals (A population is varied!!!) A population can produce far more offspring than the environment can support; those individuals that have inherited traits best suited for the environment will survive to produce offspring of their own

Population with varied inherited traits 1 Population with varied inherited traits 2 Elimination of individuals with certain traits Figure 1.6B An example of natural selection in action. 3 Reproduction of survivors

Evolution Explains the Unity and Diversity of Life Natural selection is an editing mechanism It results from exposure of heritable variations to environmental factors that favor some individuals over others Over time this results in evolution of new species adapted to particular environments

Killer whale Pangolin Pangolin Figure 1.6C Examples of adaptations to different environments. Killer whale Pangolin

THE PROCESS OF SCIENCE

Scientists Use Two Main Approaches to Learn About Nature Two approaches are used to understand natural causes for natural phenomena Discovery science—uses verifiable observations and measurements to describe science Hypothesis-based science—uses the data from discovery science to explain science. This requires proposing and testing of hypotheses

Scientists Use Two Main Approaches to Learn About Nature What is the difference between a theory and a hypothesis? A hypothesis is a proposed explanation for a set of observations A theory is supported by a large and usually growing body of evidence

Hypothesis-Based Science Poses and Tests Hypotheses We solve everyday problems by using hypotheses An example would be the reasoning we use to answer the question, “Why doesn’t the flashlight work?” Using deductive reasoning we realize that the problem is either the (1) bulb or (2) batteries. The hypothesis must be testable and falsifiable A hypothesis must be testable—find ways to check the validity of the idea. A hypothesis must also be falsifiable—find ways to reveal whether such an idea is actually not true. Teaching Tips 1. Consider using a laboratory exercise to have your students plan and perhaps conduct investigations using discovery science and/or investigations using a hypothesis-driven approach. Emphasize the processes and not the significance of the questions. Students can conduct descriptive surveys of student behavior (use of pens or pencils for taking notes, use of backpacks) or test hypotheses using controlled trials. Students will need some supervision and advice while planning and conducting their experiments. 2. Consider presenting your class with descriptions of several scientific investigations that you have written or found described in the media. Edit or include numerous examples of improper methodology (small sample size, several variables existing between the control and experimental groups, failure to specifically test the hypothesis, etc.). Let small groups or individuals analyze the experiments in class to identify the flaws. This critical analysis allows students the opportunity to suggest the characteristics of good investigations in class. 3. Have your students explain why a coordinated conspiracy promoting a specific idea in science is unlikely to succeed. Have your students describe aspects of science that would check fraudulent or erroneous claims and/or political efforts.

Test falsifies hypothesis Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burned-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Figure 1.8A An example of hypothesis-based science. Test prediction Test prediction Test falsifies hypothesis Test does not falsify hypothesis