Themes of Biology Biology 1.1 Themes of Biology Everyday, you are surrounded by living things that scientists call organisms. Some organisms; such as people, plants, animals, are obvious. Others are so small that the human eye can not see them, such as bacteria and viruses. When we try to determine what is alive and what is not we look at movement, response to environment and creation and destruction. While these characteristics may be found in many objects in our world, they do not always mean that something is alive. Biology 1.1 Themes of Biology Biology is the study of life Biologists recognize that all living things share certain characteristics; properties that separate living organisms from nonliving things. 7 unifying themes properties of life are shared by all things that are living Every living organism is composed of one or more cells is able to reproduce can obtain and use energy to run life processes will maintain a constant internal environment can pass on traits to offspring can respond and adjust to the environment will grow and develop Life is characterized by the presence of all these properties at some stage in the organisms life. All things that are living are capable of doing the following: Properties of Life What does it mean to be alive? The following properties help to define what is life; what is living and what is not living. Cellular organization Reproduction Metabolism Homeostasis Heredity Responsiveness Growth and development Unifying Themes of Biology In the study of biology, certain broad themes emerge that both unify living things and explain biology as a science. 1: cellular structure and function 2: reproduction 3: metabolism 4: homeostasis 5: heredity 6: evolution 7: interdependence Cellular structure and function All living things are made of one or more cells Cells are highly organized, tiny structures tiny structures with thin coverings called membranes Organisms can range from a single cell to trillions of cells The basic structure of cells is the same in all organisms although some cells are more complex than others Reproduction All living things can reproduce Reproduction is the process by which organisms make more of their own kind from one generation to the next. Some rapidly growing bacteria divide into offspring cells approximately every 15 minutes while bristlecone pine trees that are 5000 years old still produce seedlings. Your body contains more than 100 trillion cells which have grown from a single original cell. Metabolism Living organisms carry out many different chemical reactions in order to obtain and use energy to run their life processes. All living things use energy to grow, to move, and to develop Metabolism is the sum of all the chemical reactions carried out in an organism Metabolism Almost all energy used by living organisms is originally captured by sunlight. Plants, algae, and some bacteria capture this solar energy and use it to make complex molecules in a process called photosynthesis. These molecules than serve as the source of energy, or food, for other organisms. Metabolism Energy flows from sunlight to plants, from these plants to plant eating animals, from these animals to meat eating animals, and so on finally to humans. We extract our energy from eating a variety of plant and animal food sources. Homeostasis All living organisms must maintain a stable internal environment in order to function properly. Organisms respond to changes in their external environment and their internal processes adjust accordingly. Their bodies help them keep heat in or let extra heat escape. The maintaining of stable internal conditions in spite of changes in the external environment is called homeostasis. Homeostasis An organism unable to balance its internal conditions with its environmental conditions can become ill and die. Arctic seals are able to maintain a constant body temperature in their cold environment because of their body shape and thick layer of body fat they posses. In this way, they maintain their homeostasis or even body temperature. Heredity All living things are able to pass on traits to their offspring through genes that are passed from parent to offspring. Traits are things like hair or eye color. A gene is the basic unit of heredity. The passing of traits from parent to offspring is called heredity Heredity is the reason you resemble your parents. You inherit traits from them such as your eye color, hair color and texture and facial features. Sometimes damage causes genes to change A change in the DNA of a gene is called a mutation Mutations: Most mutations are harmful, but sometimes mutations can help an organism survive. Favorable mutations can aid an organism in survival by making it a better hunter or by making it better at avoiding predators. A fur seals white fur helps it blend into its environment and avoid hunters that may prey on it. A leopards spotted fur is a favorable mutation that helps it blend into the dappled light of a jungle rainforest. Evolution Mutations cause changes in the inherited characteristics of species over generations. Change in the inherited characteristics of species over generations is called evolution. A species is a group of genetically similar organisms that can produce fertile offspring. Individuals in a species are capable of breeding with each other and having young. A species is a group of genetically similar organisms that can produce fertile offspring Individuals in a species are similar but not identical Individuals with genetic traits that better enable them to meet natures challenges tend to survive and reproduce in greater numbers causing these traits to become more common. Charles Darwin, the 19 th century British naturalist, used the term natural- selection for the process in which organisms with favorable traits are more likely to survive and reproduce. Darwins theory of evolution by natural selection provides a consistent explanation for lifes diversity of organisms. Most scientists believe that the many different species of animals, plants, and other organisms on Earth today are the result of a long process of evolution. Interdependence Organisms in any biological community live and interact with other organisms. A biological community is a group of interacting organisms. Ecology is the branch of biology that studies the interactions with one another and with the nonliving parts of their environme nt Ecology is the branch of biology that studies the interactions with one another and with the nonliving parts of their environment Organisms are dependant on one another and on the nonliving parts of their environment; they are interdependent. Interdependence within biological communities is the result of a long history of evolutionary adjustments. The complex web of interactions in a biological community depends on the proper functioning of all its members, even those organisms too small to be seen without a microscope.