Chapter 1

Exploring Life and Science

What characteristics are shared by living organisms?

1. Organized from the atom to the biosphere2. Maintain a relatively constant internal

environment (homeostasis)3. Respond to internal and external stimuli4. Use materials and energy from the

environment5. Reproduce offspring6. Growth and development7. Evolutionary history through which

organisms change over time

How are living things organized? From Simple to Complex

• Atoms:– are the smallest chemical units

• Molecules:– are a group of atoms working together

• Organelles: – are a group of molecules working together

• Cells:– are a group of organelles working together

• Tissues: – are a group of similar cells working together

How are living things organized? From Simple to Complex

• Organs: – are a group of different tissues working

together

• Organ systems: – are a group of organs working together

• Organism: – is an individual

How are living things organized? From Simple to Complex

• Population: – Organisms of the same species in a particular area

• Community:– Interaction populations in a particular area

• Ecosystem:– A community plus the physical environment

• Biosphere:– Regions of the Earth’s crust, waters, and

atmosphere inhabited by living things

Reproducing and Growth & Development

• DNA:– Hereditary information directs:

• Structure of the Cell• Cell Metabolism

– Genes • Allow cells and organisms to make more of themselves• Direct development so that the organism resembles the parents

• Growth and Development:– Growth: increase in size and number of cells– Development:

• All changes that occur from birth to death• Repair after an injury

Homeostasis

• Homeostasis: – All body systems working together to

maintain a stable internal environment

• Systems respond to external and internal changes to function within a normal range – e.g. body temperature, fluid balance

• Failure to function within a normal range results in disease

Maintaining Normal Limits

• Receptor: – receives the stimulus

• Control center: – processes the signal and sends instructions

• Effector: – carries out instructions

Maintaining Normal Limits

Figure 1–3

Figure 1–4

Negative Feedback• The response of the effector negates the

stimulus

Positive Feedback

• The response of the effector reinforces the stimulus

Figure 1–5

Homeostasis

• Requires coordinated efforts of multiple organ systems. Any adjustment made by one physiological system has direct and indirect effects on a variety of other systems. Therefore, the use of homeostasis integrates the human body to allow for the support of life.

Evolution and Adaptation

• Evolution:– Process by which a species changes through

time– New variations arise allowing species to capture

more resources them to survive– Each successive generation include this

variation representing an adaptation to the environment

How are living organisms classified?

• Three Domains:– Eukarya, Archaea, and Bacteria

• Eukarya Kingdoms:– Vertebrate

• Animalia

– Invertebrate• Plantae, Fungi, and Protista

• Archaea Kingdom: – Archaea

• Bacteria Kingdom:– Eubacteria

How do we classify humans?

Human House Cat

Domain Eukarya Eukarya

Kingdom Animalia Animalia

Phylum Chordata Chordata

Class Mammalia Mammalia

Order Primates Carnivora

Family Hominidae Felidae

Genus Homo Felis

Species sapiens domesticus

What distinguishes humans?

1. Cultural heritage or patterns of our behavior passed from one generation to the next

2. Well-developed brains

3. Upright stance

4. Language Skills

5. Varied Tool Use

6. Modification of our environment for our own purpose which may threaten the biosphere

What do we know about Science?

1. Science is a way of knowing about the natural world

2. Science and scientists should be objective

3. Scientific conclusions may change or be modified as our understanding and technology increases

4. Science is studied using the scientific method

Science as a Process

• Scientific Theory:– Tells us about the order and the patterns in the

world– Examples:

• Cell, Homeostasis, Genes, Evolution

• Principle:– Theories that are accepted as valid by an

overwhelming number of scientists

The Steps of the Scientific Method

The Scientific Method in Action1. Observations:

- Many patients had a particular bacterium near their ulcers

2. Hypothesis:- Heliobacter pylori is the cause of gastritis and ulcers

3. Experimental/observations:- 1st : H. pylori was isolated and grown from ulcer patients- 2nd : Humans swallowing a H. pylori solution resulted in

inflammation in their stomachs

4. Conclusion:- H. pylori was the cause of most ulcers and can be cured

by antibiotics

A Controlled Study• Variables:

– Experimental variable is the variable that is purposely changed or manipulated

– All other variables need to remain constant

• Groups:– Test group is a group of subjects that are exposed

to the experimental variable– Control group is a group for comparison that is not

exposed to the experimental variable

Reading about scientific information

• Scientific journals are considered the best source of information but can be difficult for the lay person to understand

• Often the lay person reads secondary sources and must be wary of information taken out of context

• Be careful of information on the Internet by using reliable sources such as URLs with .edu, .gov and .org

What should you look for when you read about science?

• Beware of anecdotal data• Understand methodology and results• Does the data justify the conclusions inferred

by the scientists?• Be able to read a graph• Have some understanding of statistics

– Standard Error (example 5 ± 1)– Statistical Significance (P< 0.5)

• Possibility that the results are due to some other factor other than the experimental variable

Does science have social responsibilities?

• Science is a way of acquiring knowledge about the natural world through a systematic process separating it from ethics, religion and aesthetics

• Technology is the application of scientific knowledge to human interests- Biotechnology (genetically modified crops)- Gene technology (cloning of humans or gene therapy

to modify inheritance)- Use of stem cells from embryos