introduction to biology to be taught earlier

Introducing Biology

• Nature of Biology: The Characteristics of Life

• The Scientific Method

The Nature of Biology

• Biology is the study of life

– Life defines animate from inanimate

• Humans from Rocks

• A Donkey from a Chair

Universal similarities

• Humans, cats, bacteria, stones, gravel and brick are all made up of atoms – the building blocks of matter

• All have their very basic components in the subatomic particles: protons, electrons and neutrons.

How do we differ?

• The key difference is the difference between matter and molecules

– Stones and gravel consist of matter

– Biological living beings are made up of organic molecules

Organic molecules: the basic cellular components:

• DNA and RNA

• Proteins

• Lipids

• Carbohydrates

The cell is the smallest unit having the capacity for life and

ALL living things consist of one or more cells

And all cells are made up of organic molecules

The Characteristics of Life

• Organisms consist of one or more cells

– Assembled by same kinds of atoms and molecules according to the same laws of energy

The Characteristics of Life

• Organisms produce and expend energy (=metabolism)– Cells obtain and convert energy from their

surroundings (photosynthesis and aerobic respiration)

– Cells use energy to maintain themselves (assemble, stockpile, breakdown and dispose of necessary cellular materials)

The Characteristics of Life

• Organisms sense changes to their environment and make controlled responses– Each organism has receptors (molecules and

structures that can detect specific stimuli)– A stimulus is any energy change in the

environment (light, heat, etc.)

The Characteristics of Life

• Organisms have the capacity for growth– Development occurs in higher organisms

(zygote to multicellular)– Growth is regulated (not unlimited)

The Characteristics of Life

• Organisms have capacity for reproduction– Based on heritable instructions encoded in the

molecular structure of their DNA– Sexual reproduction provides the diversity of

organisms

The Characteristics of Life

• Organisms die– Sad but true

Biological systems are organized into a series of levels, with the units at one level forming the components or building blocks of the next.

Hierarchy of Life

• Subatomic particles– Protons, electrons, neutrons

• Atom– Smallest unit of an element

• Molecule– Two or more atoms bonded together

Hierarchy of Life

• Organelle

– Membrane bound sac or compartment found inside all cells but bacteria

• Cell

– Smallest unit that can live and reproduce independently

Hierarchy of Life

• Tissue

– An organized group of cells and surrounding substances functioning together in a specialized activity

• Organ

– A group of specialized tissues that together provide a specific function

Hierarchy of Life

• Organ system

– 1 of more organs which interact chemically and/or physically

• Multicellular organism (e.g., us, dog)

– An individual composed of specialized, interdependent cells

Hierarchy of Life

• Population

– A group of individuals of same species occupying a given area

• Community

– The populations of all species occupying a given area

Hierarchy of Life

• Ecosystem

– A community and its physical environment 

• Biosphere (EARTH)

Hierarchy of Life

• Organisms connect with one another by a one-way flow of energy through them and a cycling of materials among them.

• The flow of energy starts with the producers – plants and other organisms capable of making their own food via photosynthesis.

Hierarchy of Life

• Consumers (animals) depend on the energy obtained by producers (either directly by eating plants or indirectly by eating animals that eat plants).

• Decomposers break down biological molecules and this energy is available to the producers (nutrients).

Hierarchy of Life

• The interconnectedness of organisms affects the structure, size, and composition of populations and communities – which affects ecosystems and the biosphere.

The Scientific Method

How we know what we know

The Nature of Biological Inquiry

• SCIENTIFIC METHOD in the study of biological and physical phenomena: The process involves observing phenomena, asking questions based on these observations, devising a tentative explanation, and performing experiments to support or refute this explanation.

Scientific method involves:

• Make an observation - noting a specific phenomenon in nature. – The observations must be systematic and

objective.

• Devise a working hypothesis - coming up with a tentative explanation for the specific phenomenon. – One must explain observations using only

known chemical and physical laws.

Scientific method involves:

• Make a testable and falsifiable prediction - making a claim about what can be expected based on your hypothesis– Note: For statistical reasons, we actually test

hypotheses by constructing and testing their converse, the null hypothesis. Rejecting a null hypothesis supports the working hypotheses. By contrast, accepting a null hypothesis suggests there that our hypotheses is invalid.

Scientific method involves:

• Testing the hypothesis/prediction - an attempt to produce actual observations that match predicted observation

– involves defining variables to test and collecting unbiased data.

= Experimental Design

Experimental Design

•  clearly define independent, dependent and standardized variables:– independent variable: the factor being

manipulated in the experiment– dependent variable: that variable which

responds to the manipulation– standardized variable: all the variables that are

held constant between the variables.

Experimental Design

• Define the experimental treatment: – A treatment is a test group of individuals that

are subjected to the same levels of the independent variable.

• Define the control group:– The control group consists of individuals that

receive no treatment but are held to the same standardized variables.

Experimental Design

• Select materials and identify experimental methods and methods of data collection.

• Use replications – scientific conclusions are statistical

Scientific method involves:

• Perform experiments and collect data in a precise and unbiased manner.

• Analyze Data Statistically– Because results are never absolute, we must

determine the probability that our null hypothesis is true or false. That is, we attempt to generalize from our finite sample to the world at large. This relies on statistical analysis of the data.

Scientific method involves:

• Re-Evaluate Hypotheses and Report– We can never prove that a hypothesis is true.

Instead, hypotheses are supported when a number of experiments do not falsify it.

If we reject our hypothesis:

• Error in data

• Missing observations

• Predictions based on hypothesis may be flawed

• Hypothesis itself may be flawed – data do not support hypothesis (therefore must alter hypothesis and continue experimentation).

Key Elements of a Scientific Approach

• Criteria for an explanation to be considered scientific: – Must explain observations using only known

chemical and physical laws – Must make testable predictions – Must be falsifiable

Key Elements of a Scientific Approach

• Important components of the scientific method: – Working hypothesis – Null hypothesis – Experimental design