Invitation to Biology: Levels of Organization

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I NVITATION TO B IOLOGY

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1. Levels of organization

2. The basis of inheritance

3. Energy and life’s organization

4. Evolution and diversity

5. The nature of biological enquiry

6. Scientific experiment

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¢ All matter consists of atoms, which combine as molecules.

¢ Organisms are individuals that consist of one or more cells.

¢ Cells of larger multi-celled organisms are

organized as tissues, organs, and organ systems.

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EVELS OF ORGANIZATION

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Atoms is the fundamental building block of all substances (living and non-living),

joined together to form molecules (exp:

carbohydrate, lipids, proteins, DNA, RNA..etc).

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Many molecules are organized as cells, the smallest subunit of life that can survive and reproduce based on information in DNA, energy inputs, raw materials.

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In multi-celled organisms, trillion of cells organized into tissues to carry out a specific function. Exp: Connective tissue, muscle

tissue, epidermis tissue.

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Organs are formed by the functional grouping together of multiple tissues to

serve a common function (exp: Heart (cardiac tissue + sporadic tissue + connective tissue).

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Two or more organs working together for a specific body function, form an organ

system (also known as biological system or body system).

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Organism is any contiguous living system, capable of response to stimuli,

reproduction, growth and development.

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Population is a group of individuals of the same kind of organism, or species, in a specific area.

Exp: Blue fin tuna in the Indian Ocean

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A community consists of all populations of all species in a specified area.

Exp: Coral reef community of the Indian Ocean

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A community that is interacting with its physical environment through inputs and outputs of energy and materials.

Exp: Coral reef ecosystems flourish in

warm, clear sea water in the Indian Ocean.

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¢ The Science of Nature

We understand life by studying it at different levels of organization, which extend from atoms and molecules to the biosphere.

The quality we call “life” emerges at the level of cells.

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¢ To carry on life processes, an organism must have:

Precise instructions;

Communication among cells through chemical substances and electrical impulses.

¢ DNA:

Contains instructions, necessary for cells to make proteins.

The signature molecule of life which provides the basis of growth, survival and reproduction.

Source of each organism’s distinct features, or traits.

Usually a double-helix and has two strands running in opposite directions.

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HE BASIS OF INHERITANCE

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¢ DNA makes up genes that code for polypeptides (protein) which functionally important for the organisms.

¢ Proteins determine the structure and function of cells and tissues.

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The basis of inheritance

¢ Link to video: Protein synthesis

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¢ Cell-to-cell communication is a critical and complex process called cell signaling.

¢ Information transmitted from one part of the body to another is important in regulating life processes

¢ Information is transmitted by:

Hormones

Neurotransmitters and their receptors

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OMMUNICATION BETWEEN CELLS

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¢ Living organisms need energy and nutrients to keep the body’s functions.

Energy is the capacity to do work, that is generated through cellular respiration.

Nutrient is a particular type of atom or molecule that has an essential role in growth and survival.

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NERGY AND LIFE

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¢ Different organism may obtain their energy and nutrients differently.

¢ The differences allow us to put organisms into one or two broad categories: producers or consumers

¢ Producers (exp: plants):

Get energy and simple raw materials from environmental sources and make their own food (through photosynthesis in plants)

¢ Consumers:

Can’t make their own food and they get energy and nutrients indirectly by eating producers and other organisms

¢ Producers and consumers cycle their nutrients among themselves (?).

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¢ Energy is not cycled.

¢ Energy flows through the world of life in one direction- from the environment through producers, then through consumers.

¢ It is a one way flow, because with each transfer, some energy escapes as heat.

¢ Cells do not use heat to do work.

¢ Thus, energy that enters the world of life ultimately leaves it permanently.

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¢ Question: Who is the producer?

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¢ Question: Who is the producer?

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¢ Individuals of a population are alike in certain aspect of their body form, function and behavior…But, rarely that these traits are exactly alike.

¢ Exp: Over 7 million individuals of the human species shows variation in many traits.

¢ Why?

¢ Variations in most traits arise through mutations or changes in DNA.

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VOLUTION AND DIVERSITY

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¢ Mutations create adaptive traits.

More likely to survive and pass on its DNA to offspring.

¢ Charles Darwin:

Natural population tends to increase in size, therefore creates higher competition for limited resources.

Adaptive forms of traits make their bearer more competitive and become more common over generations.

The differential survival and reproduction of individuals in a population that differ in the details of their heritable traits is called natural selection.

¢ Artificial selection through selective agents.

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¢ In biology, evolution means change in a line of descent.

¢ Evolutionary processes and events underlie life’s diversity.

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¢ Taxonomy is the science of naming and classifying organisms.

¢ Binomial systems of nomenclature:

Developed in the 18th century by Linnaeus, a Swedish botanist

Names and classifies organisms

Basic unit is a species

Each species assigned a two part name

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¢ Critical thinking means systematically judging the quality of information as you learn its content and implications.

¢ Science looks for natural explanation of objects and events. It does not address supernatural…

¢ Explanations must be testable in the natural world in ways that others can repeat.

¢ Scientists make potentially falsifiable predictions about how the natural world works. They search for evidence that may disprove an explanation.

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HE NATURE OF BIOLOGICAL ENQUIRY

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CIENTIFIC EXPERIMENT

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¢ Scientific experiments can simplify the study of a

complex natural process by restricting the researcher’s focus to a single aspect of that process.

Example: Water in Lake X is green and smelly.

Why?

¢ Researchers try to design experiments carefully in order to minimize the potential for bias.

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¢ Experiments cannot be performed on all individuals of a group or in each part of the places where organisms live.

¢ Experiment on subsets of a population, event, or some other aspect of nature that they select to represent the whole.

¢ Sampling error and bias in scientific experiments:

Is a difference between results from a subset and results from the whole.

More serious when sample sizes are small.

Large samples or repeating the experiment may reduce error or bias.

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