1. Chapter 1 – Biology: Exploring Life
General Biology (Bio107)
Chapter 1 – Biology: Exploring Life

2. Introduction
Biology, the study of life, is rooted in the human spirit.
Biology is the scientific extension of the human tendency to connect to and be curious about life.
Biology is one of the sciences takes us:
Into a variety of environments to investigate ecosystems
To the laboratory to examine how organisms work
Into the microscopic world to explore cells and the submicroscopic to explore molecules in cells
Back in time to investigate the history of life.

3. This is an exciting era for exploring biology.
Biology is both – a body of knowledge & an ongoing inquiry process to enhance it.
This is an exciting era for exploring biology.
The largest and best-equipped community of scientists try to solve problems that once seemed insolvable.
Genetics and cell biology are revolutionizing medicine and agriculture.
Molecular biology provides new tools to trace the origins and dispersal of early humans.
Ecology is helping evaluate environmental issues.
Neuroscience and evolutionary biology are reshaping psychology and sociology.

4. Unifying themes pervade all of biology
Life’s basic characteristic is a high degree of order build with materials based on carbon.
Biological organization is based on a hierarchy of structural levels, each building on the levels below.

5. Hierarchical levels of life
Atoms
Molecules
Organelles
Cells
Tissues & Organs
Organisms
Populations
Communities
Ecosystems & Biosphere
Invisible
Visible

6. Atoms & Molecules
At the lowest level are atoms of diverse chemical elements.
Atoms are ordered via bonds into larger, complex biological entities called molecules.
Many molecules are arranged into minute structures called organelles, which are crucial functional components of cells.

7. Cells are the smallest living structures of organisms; they are the living units of life.
Some organisms consist of single cells, others are multicellular aggregates of specialized cells.
Whether multicellular or unicellular, all organisms must accomplish the same functions: uptake and processing of nutrients, excretion of wastes, response to environmental stimuli, and reproduction among others.

8. Tissues
Similar cells are grouped into tissues to fulfill certain biological functions.
In multicellular organisms several tissues coordinate to form organs, and several organs form an organ system.
For example, to coordinate
locomotory movements,
sensory information travels
from sense organs to the brain,
where nervous tissues composed
of billions of interconnected neurons,
supported by connective tissue,
coordinate signals that travel via
other neurons to the individual muscle cells.

9. Organisms & Populations
Biological organisms belong to larger populations, i.e., a localized group of organisms belonging to the same species.
Populations of several species in the same environment comprise a biological community.
These populations interact with their physical environment to form an ecosystem.

10. Biology: The study of life
Investigating life at its many levels is fundamental to biology.
Biological processes often involve several levels of biological organization.
The coordinated strike of a rattlesnake at a mouse requires complex interactions at the molecular, cell, tissue, and organ levels within its body.
Many biologists study life at one level but gain a broader perspective when integrating discoveries with processes at other levels.

11. Life & Emergent properties
While studying life, novel properties emerge at each step upward in the biological hierarchy.
These emergent properties result from interactions between components.
A cell is certainly much more than a bag of molecules.
This theme of emergent properties accents the importance of structural arrangement.
The emergent properties of life are not supernatural, but simply reflect a hierarchy of structural organization.

12. Life resists a simple, one-sentence definition, but we can recognize life by what living things do; life has defining properties.

13. Is this “Fulgurite” alive?
How do you know you deal with life?

14. The properties of life
Complex structures - made of chemical elements, mostly carbon (C)
Metabolism - the sum of all chemical reactions - anabolism & catabolism
Homeostasis - capacity to maintain internal balance
Responsiveness
- living organisms are able to react to external stimuli, e.g. light, cold, heat, with the help of sensory mechanisms, tissues or organs

15. The properties of life
5. Development & Growth - living organisms develop from simple small structures, e.g. spores, seeds, eggs, cells, into more complex or multiple structures

16. Properties of life
6. Reproduction - living organisms are able to form new (daughter) organisms and new generations with the help of the hereditary molecule DNA Capacity to evolve

17. The diversity of life Diversity is a hallmark of life.
At present, biologists have identified and named about 1.5 million species.
This includes over 280,000 plants, almost 50,000 vertebrates, and over 750,000 insects.
Thousands of newly identified species are added each year.
Estimates of the total diversity of life range from about 5 million to over 30 million species.

18. Taxonomy
Biological diversity is something to relish and preserve, but can be a bit overwhelming.
Despite its complexity, biologists have categorized life into a smaller number of groups through taxonomy.
Taxonomy is the branch of biology that names and classifies species into a hierarchical order.

19. The diversity of life
More than 1.5 million different species are known
Biologists ordered - or classified – life’s huge diversity into three domains and six major kingdoms

20. The six kingdoms of life

21. New methods, including comparisons of DNA among organisms, have led to a reassessment of the number and boundaries of the kingdoms.
Below the kingdom level biologists introduced phyla, classes, orders, families and genera
At the lowest level is the species concept

22. Life: Unity in diversity
Despite the enormous diversity there is much unity in life.
All life forms are made up from cells. - prokaryotic & eukaryotic cell types exist - cell theory postulates that all living things consist of cells.
The hereditary molecule of all forms of life is DNA. - DNA is the substance of genes, the units of inheritance that transmit information from parents to offspring.

23. All forms of life employ the same genetic code made up from 64 chemical codons. - The diversity of life is generated by different expressions of a common chemical language for programming biological order.
All life forms assure growth by performing highly similar DNA copying and cell division processes. - DNA replication, mitosis (eukaryotic) & binary fission (prokaryotic)
All life forms use ribosomes to translate the genetic code of genes into proteins

24. All life forms use biological catalysts called enzymes to drive their many chemical reactions, i.e. metabolism.
All life forms posses regulatory control mechanisms which assure homeostasis. - positive and negative feedback mechanisms - negative feedback slows processes down

25. All life forms exist as open systems that exchange energy and materials with their surrounding environment. - leaves absorb carbon dioxide from the air, water from the soil and capture the energy of light to drive photosynthesis; in exchange oxygen is released - the exchange of energy between an organism and its surroundings involves the transformation of energy from one form to another while heat is released

26. Strong correlation of structure and function in life forms at all levels of biological organization
E.g. structure-function relationship in the aerodynamic efficiency in shape of bird wing.
Honeycombed internal structure produces light but strong bones.
Neurons control flight muscles.
Many mitochondria provide the energy to power flight.

27. All life forms evolve.
Evolution is the key to understanding biological diversity. Evolutionary connections among all organisms explain the unity and diversity of life.
Evolution is the core theme of biology.
It accounts for this combination of unity in diversity of life.

28. Since life evolves, each species is one twig on a branching tree of life extending back through ancestral species, living and extinct.
The history of life is a saga of a restless Earth billions of years old, inhabited by a changing cast of living forms.

29. All life is connected through evolution.
Species that are very similar share a common ancestor that represents a relatively recent branch point on the tree of life.
Brown bears and polar bears share a recent common ancestor.
Both bears are also related through older common ancestors to other organisms.
The presence of hair and milk-producing mammary glands indicates that bears are related to other mammals.
Similarities in cellular structure, like cilia, indicate a common ancestor for all eukaryotes.
All life is connected through evolution.

30. Charles Darwin brought evolutionary biology into focus in 1859 when he presented two main concepts in The Origin of Species.
1. Contemporary species arose from a succession of ancestors through “descent with modification” (evolution).
2. The mechanism of evolution is natural selection.

31. The process of science
The word science is derived from the Latin verb ‘scientia’ meaning “to know”.
At the heart of science are people asking questions about nature and believing that those questions are answerable.
The process of science blends two types of exploration: discovery science and hypothetico-deductive science.

32. Science seeks natural causes for natural phenomena.
The scope of science is limited to the study of structures and processes that we can observe and measure, either directly or indirectly, e.g. through experimentation.
Verifiable observations and measurements are the data of discovery science.

33. Discovery science can lead to important conclusions via inductive reasoning.
An inductive conclusion is a generalization that summarizes many concurrent observations.
The observations of discovery science lead to further questions and the search for additional explanations via the scientific method.

34. Scientific inquiry process
The scientific method consists of a series of steps.
Few scientists adhere rigidly to this prescription, but at its heart the scientific method employs hypothetico-deductive reasoning.

35. Role of hypothesis
A hypothesis is a tentative answer to some question (“proposed explanation”).
The deductive part in hypothetico-deductive reasoning refers to the use of deductive logic to test hypotheses.
Most hypothesis are tested by performing a scientific experiment to see whether or not the results are as predicted.
Deductive logic takes the form of “If…then” logic.
Reasoning flows from general to specific.

36. Experimental controls
A “good” scientific hypothesis has to be testable (‘verifiable’), falsifiable and based on causality.
Scientists use controlled experiments to make comparisons between two sets of subjects, e.g. patients +/- drug.
The set that receives the experimental treatment (drug) is the experimental group.
The control group receives all variables as the experimental group except the control variable (= drug).
Controlled experiments enable scientists to focus on responses to the change of a single variable.

37. Scientific theory
Facts, in the form of verifiable observations and repeatable experimental results, are the prerequisites of science.
Science advances when several observations and experimental results that seemed unrelated are tied together in a theory.
A scientific theory is broader in scope, more comprehensive, than a hypothesis.
They are only widely accepted in science if they are supported by the accumulation of extensive and varied evidence.

38. Scientific theories are not the only way of “knowing nature”.
Various religions present diverse legends that tell of a supernatural creation of Earth and its life.
Science and religion are two very different ways of trying to make sense of nature.
Art is another way.
Biology showcases life in the scientific context of evolution, the one theme that continues to hold biology together no matter how big or complex the subject becomes.

39. Facts, in the form of verifiable observations and repeatable experimental results, are the prerequisites of science.
Science advances when: 1. A new theory ties together several observations and experimental results that seemed unrelated previously.
2. New technologies are applied to answer old questions.
A scientific theory is broader in scope, more comprehensive, than a hypothesis.
Both are only accepted in science if they are supported by accumulation of extensive and varied evidence.

40. Both cooperation and competition characterize the scientific culture.
It is not unusual that several scientists are asking the same questions using different approaches, e.g. techniques.
Scientists build on earlier research and pay close attention to contemporary scientists in the same field.
They share information through publications, seminars, meetings, and personal communication.
Both cooperation and competition characterize the scientific culture.
Scientists check each other’s claims by attempting to repeat experiments.
Scientists are generally skeptics.

41. Some philosophers of science argue that scientists are so influenced by cultural and political values that science is no more objective than other ways of “knowing nature”.
At the other extreme are those who view scientific theories as though they were natural laws.
The reality of science is somewhere in between.
The cultural milieu affects scientific fashion, but need for repeatability in observation and hypothesis testing distinguishes science from other fields.
If there is “truth” in science, it is based on a preponderance of the available scientific evidence.

42. Science & Technology Are associated and are functions of society.
Technology results from scientific discoveries applied to the development of goods and services.
DNA technology and biotechnology has revolutionized the pharmaceutical industry.
It also has an important impact on agriculture and the legal profession.
E.g. genetic engineering enables scientists to transplant foreign genes into microorganisms and mass-produce valuable products.

43. Not all of technology is applied science.
Technology predates science, driven by inventive humans who designed inventions without necessarily understanding why their inventions worked.
The direction that technology takes depends less on science than it does on the needs of humans and the values of society.
Technology has improved our standard of living, but also introduced new problems.
Science can help us identify problems and provide insight about courses of action that prevent further damage.

44. Both science and technology have become powerful functions of society.
It is important to distinguish “what we would like to know” from “what we would like to build.”
Scientists should try to influence how scientific discoveries are applied.
Scientists should educate politicians, bureaucrats, corporate leaders, and voters about how science works and about the potential benefits and hazards of specific technologies.