BIOLOGY The Study of Life

Biologists study questions about How living things work How they interact with their environment How they change over time

Biologists actively work to solve real world problems such as Improving our food supply Curing disease Preserving our environment

Characteristics of Life Organization and cells Response to Stimuli HomeostasisMetabolism Growth and Development Reproduction Change through time

Organization and cells -all living things, whether made up of one cell or many cells have some degree of organization Cells- smallest unit that can perform life’s functions Unicellular-organisms composed of one cell Multicellular-organisms that are made up of more than one cell

Levels of Organization

Response to Stimuli Organisms can respond to a stimulus- a physical or chemical change in the internal or external environment Organisms must be able to respond and react to changes in the environment to stay alive Example: An owl’s eyes dilate when it gets dark to help them see better

Homeostasis The maintenance of a stable level of internal conditions even though environmental conditions are constantly changing Example: Owl’s feathers fluff up in the cold to trap a layer of insulating air next to their bodies

Metabolism The sum of all the chemical reactions in the body Example: An owl’s metabolism allows the owl to extract and modify the chemicals trapped in its nightly prey and use them as energy to fuel activities and growth

Growth and Development The growth of living things results from the division and enlargement of cells Development is the process by which an organism becomes a mature adult A human body is composed of trillions of specialized cells which originated from a single fertilized egg

Reproduction Reproduction, unlike the other characteristics, is not essential to the survival of an individual organism Reproduction is essential for the continuation of the species Organisms transmit hereditary information, DNA, to their offspring Gene- is a short segment of DNA that contains the instructions for one trait During sexual reproduction, hereditary information recombines from two organisms from the same species In asexual reproduction one organism is able to make an identical copy of itself

Change through Time - EVOLUTION Organisms change slowly over time as their environment changes This factor helps us explain the diversity of life forms we see today

THEMES Of LIFE DiversityUnity InterdependenceEvolution

Diversity Variety There are single celled and multi- cellular organisms There are organisms that live in ice and ones that live in hot springs We have identified more than 1.5 million species on Earth, with many more still to be identified

Unity Features that all living things have in common Genetic code Organelles that carry out all cellular activities All living things share certain genes, but no two types of organisms have the same full set of genes

DOMAINS OF LIFE Three Domains of Life Bacteria- prokaryotes (simplistic organism) found in more common environments Archae- prokaryotes (simplistic organisms) that live in extreme environments such as hot springs, high salinity ecosystems Eukarya- consists of protists, fungi, plants, and animals

Interdependence of Organisms Ecology - studies organisms interacting with each other and with the environment Ecosystems - communities of living species and their physical environment Organisms depend on each other, minerals, nutrients, water, gases, heat, and other aspects of the physical world Example: a panther eats a bird, which eats nuts from a tree. The tree needs carbon dioxide and water. Carbon dioxide is a main byproduct of all animals

Humans have had a huge impact on the world’s environment We have cleared vast areas of the rain forests for the rare wood that grows only there. The rain forests are the biggest filters of greenhouse gases on our planet

EVOLUTION of LIFE (descent with modification) - the process in which the inherited characteristics within a population change over generations Natural selection- organisms that have certain favorable traits are better able to survive and reproduce successfully than organisms that lack these traits Adaptations are traits that improve an individual’s ability to survive and reproduce Example: Rabbits with white fur and short ears living in a snowy place as opposed to somewhere that gets no snow