introduction notes

Introduction

All Materials © Cmassengale

Study of Life

First life forms arose on Earth more than 3.5 billion years ago
Single-celled, microscopic organisms (living thing) appeared first & floated alone in seas
Over 40 million species (types of organisms) exist with only about 2 million identified
Many organisms are unidentified & new species are still discovered
Biology is the study of all living things and how they interact with each other & their environment
Over long periods of time, species changed or evolved so that new species arose from earlier organisms & came to inhabit almost every part of the earth (bacteria living in thermal vents, parasites living inside another organism, etc.)
Organisms must adapt to their specific environment to survive & reproduce

Unifying Themes of Biology

The six unifying themes include:

Cell Structure & Function

Cell is the basic unit of structure & function
All organisms are made of one or more cells; Unicellular (one celled) or Multicellular (Composed of more than one cell)

UNICELLULAR AMOEBA

Cells are small but highly organized; they contain specialized structures that carry out the jobs of a cell called organelles

CELLULAR ORGANELLES

There are many different kinds of cells, but all cells have similarities
All cells are surrounded by a cell membrane, contain cytoplasm, and have DNA (the genetic information for making new cells or cell structures)
New cells made by unicellular organisms are identical (clones) to the parent cell that produced them – asexual reproduction
Multicellular organisms begin life as one fertilized cell (sexual reproduction), but the cells multiplied and underwent differentiation (changed structure & function) to become many different kinds of cells

Stability & Homeostasis

All organisms maintain stable internal conditions such as body temperature & water content
Stable level of internal conditions called homeostasis

Reproduction & Inheritance

All organisms reproduce new organisms like themselves by transmitting hereditary material to their offspring
DNA (Deoxyribonucleic acid) is a large molecule containing the hereditary material of the cell

DNA MODEL

In unicellular organisms like bacteria, DNA exists as a single loop or chromosome in the cytoplasm

BACTERIA

In multicellular organisms, DNA is enclosed in a membrane known as the nucleus
Genes are short segments of DNA the carry the instructions for a single trait of an organism
DNA of a cell contains all of the genes (instructions) it will ever need
All body cells have a complete set of DNA (genome), but different types of cells use certain genes from the set; example: Muscle cells have the genes to make thyroxine, but they don’t use these genes
In sexual reproduction, an egg (ovum) is fertilized by a sperm to form a zygote so the new organism is made of cells with hereditary information from both parents
In asexual reproduction, cells copy their DNA & split so all new cells are identical

Evolution

DARWIN - THEORY OF EVOLUTION

Natural selection or “survival of the fittest” is the process that drives evolution
Organisms with favorable traits are better able to survive & reproduce
The survival of organisms with favorable traits causes a gradual change in populations of organisms over many generations
Evolution by natural selection is driven by competition for resources such as food, habitat, mates

Interdependence of Organisms

Ecology is the study of the interaction of organisms with each other and their environment
Sunlight is the ultimate energy for all organisms
Energy from the sun is passed from one organism to another; producers (plants) to herbivore (plant eater) to carnivore (meat eater) to decomposers (break down dead organisms)

ENERGY FLOW IN A FOOD CHAIN

Abiotic (nonliving factors) such as air, water, energy, soil, temperature, & minerals are also needed for survival
Biotic factors include all living things on earth (plants, animals, fungi, microorganisms)
Biosphere supports life & includes the biotic (all organisms) & the abiotic (all nonliving factors) on earth
Organisms respond to their environment by:
* Fleeing
* Adapting
* Dying
Most organisms can survive a temporary change, but permanent change can lead to extinction (dinosaurs)
Thousands of species are listed endangered (population so small could become extinct)
Human interference is the main cause for endangerment & extinction
* Pollution of land, air, and water
*Hunting for sport, food, and commercial products also threatens the survival of many organisms
* Clear-cutting rain forests
* Diverting rivers & lakes
* Draining wetlands (everglades)
*Global Warming
Endangered organisms can be protected & returned to larger population size (American Bison almost wiped out –60 million to 250 in 90 years- now several thousand herds)

AMERICAN BISON

Species is a group of organisms so similar to one another that they can interbreed & produce fertile offspring
Extinction of any species upsets the balance of nature (Almost extinct Pacific Yew tree found to contain chemical used to treat cancer)

PACIFIC YEW TREE

Matter, Energy, & Organization

Organisms are highly organized, maintain internal order, & require a constant energy supply
Plants & unicellular organisms with chlorophyll capture sunlight through photosynthesis & store it in food to be used by other organisms
Autotrophs or producers use sunlight, water, & carbon dioxide to make glucose (energy rich sugar) & oxygen – photosynthesis

Heterotrophs (consumers) feed on producers or other consumers to get energy & release carbon dioxide

Biology affects life in many ways

Biotechnology uses organisms to make products needed by people (human insulin made by bacteria)
Fossils fuels (coal, oil, & natural gas) provide energy & materials such as nylon & polyester

OIL DRILLING

Animal products such as wool, silk, and leather make clothing
Wood provides energy & shelter for us, but endangers other animals (spotted owl) when forests are cut
New medicines, better water treatment & garbage disposal improves our health