The Characteristics of Life AP Biology Notes: #1
Life s Diversity & Unity Life has extensive diversity. Despite its diversity, all living things are composed of the same chemical elements that make-up non-living things. Yet, all living things have fundamental characteristics that they share and help distinguish from non-living things.
The Characteristics of Life Biologists have devised a list of 8 characteristics that all life shares. Something can be considered alive ONLY if it displays ALL 8 of these characteristics. Anything that possesses all 8 of the characteristics of life is called an organism.
The 8 Characteristics of Life: 1. Organization/Order has cellular organization (all organisms are made of 1 or more cells) cell tissue organ system organism 2. Reproduces DNA is the common genetic material 3. Growth & Development 4. Metabolism acquires materials for energy 5. Responds to Stimuli responds to the environment 6. Homeostasis/Regulation maintains internal balance 7. Evolutionary Adaptations As a group, organisms adapt and change over time. 8. Organic Carbon is the basis of all biological molecules found in living organisms
The Characteristics of Life 1. Life has Cell(s) & is based on Cellular Organization: All life begins with the cell. Cell = smallest unit of life. In multi-cellular organisms, similar cells cluster together to form tissues. "Omnis cellula e cellula (Every cell out of a cell) Rudolf Carl Virchow (1821 1902)
A Hierarchy of Biological Organization The hierarchy of life extends through many levels of biological organization The levels: Atom Molecule Cell Tissue Organ System Organism Population Community Ecosystem Biosphere
Emergent Properties Each new level of biological organization has emergent properties. Emergent Properties = features that result due to interactions between parts making up the whole that do not exist in the parts alone. IN THE LIVING WORLD, THE WHOLE IS INDEED MORE THAN THE SUM OF ITS PARTS.
The Characteristics of Life 2. Life reproduces: All living organisms are able to produce live offspring. Life comes from life! SPECIES = group of organisms that can breed & produce fertile offspring Sexual Asexual
DNA/Genes All living organisms contain genetic information that can be passed on through generations. Each offspring s DNA is unique!
3. Life Grows & Develops: All living organisms grow & develop during their life spans. Growth: an increase in the size or mass of an organism due to an increase in the size & number of cells Development: all of the changes that take place throughout the life span of an organism
The Characteristics of Life 4. Life requires Energy/Metabolism: Life acquires, stores, & processes nutrient molecules from food for energy. PRODUCERS: most plants & some unicellular organisms use solar energy to make their own food & fuel their activities. CONSUMERS: organisms that cannot make their own food get energy by consuming other organisms.
What is Metabolism? All chemical reactions in the cell that make parts or products from nutrient molecules to utilize or create energy. Two Types: Anabolism = synthesis reactions (to produce & store energy) Catabolism = breaking down reactions (to release energy)
Here Comes the Sun ULTIMATE SOURCE OF ENERGY = SUN! Photosynthesis = process of transforming solar energy into chemical energy stored in the chemical bonds between organic nutrient molecules Cellular Respiration = process of acquiring energy by metabolizing nutrient molecules produced by photosynthesis Byproducts of each support the other!
The Characteristics of Life 5. Life Responds to Stimuli: Living things have the ability to react (or respond) to an environmental condition or stimulus. Physiological or Behavioral Response often results in movement Necessary to help ensure survival of the organism & help it to carry out daily activities or behaviors.
What is Stimuli? Stimulus = anything in the internal or external environment that causes a response Response = reaction to a stimulus; can be a behavior change or physical and/or chemical response Venus flytrap
The Characteristics of Life 6. Maintains Homeostasis: All living organisms are able to maintain a relatively constant internal environment or condition. Homeostasis: the regulation of an organism s internal environment within certain boundaries to maintain conditions suitable for life.
Organisms maintain homeostasis Behavior by depending on: Innate Control Mechanisms Release of Enzymes, Hormones, Nerve Impulses, etc. Positive & Negative Feedback Mechanisms are Essential for Internal Regulation: Organisms maintain dynamic balance by switching on & off physiological pathways Pathways can create products that stimulate new pathways or even shut themselves off.
The Characteristics of Life 7. Life Adapts and Evolves: Living things must adapt to their environment to survive. If a trait is advantageous, it becomes an adaptation. it can help some individuals survive it is passed on to future generations. OVER LOTS OF TIME, the population s genes can change/evolve because more individuals have the adaptation.
Adaptation = an inherited trait that gives an advantage to organisms in their environment & is passed on Evolution = changes in the genetic make-up of an organism over time Evolution occurs by natural selection of adaptations.
Clarifying Evolution, Adaption, and Natural Selection Evolution = the theory on how changes in a population (i.e. group of interbreeding species) occurs over extended time assumes that the how or mechanism by which adaptations occur in a species is natural selection Natural Selection = the mechanism by which evolutionary adaptations occur over time in response to a population s environment Adaptation = the product of natural selection; a trait or physical modification that makes organisms better suited for their environment
Evolutionary View on Life Began in 1859 when Charles Darwin published On the Origin of Species by Natural Selection Origin of Species Highlighted: Natural Selection Descent with Modification Figure 1.18
When Natural Selection Occurs A population s have heritable variations or traits. exposed to the environment all the time. Selection occurs when traits in a population give an organism an advantage for survival and successful reproduction. Thus, selection is when heritable variations favor the reproductive success of some individuals over others.
Products of Natural Selection Are exquisite adaptations of organisms to the special circumstances of their way of life and their environment
Evolution Supports the Theme of Descent with Modification Descent with Modification explains why life has both unity and diversity. UNITY: All organisms share common defining features of life, suggesting they descended from a common ancestor DIVERSITY: The process of evolution allows species to modify features in order to adapt to different ways of life. This allows for life to be diverse.
The Characteristics of Life 8. Life is ORGANIC: Living organisms are made of molecules with lots of Carbon atoms!
Carbon the stuff of life Organic molecules contain a variety of atomic elements. i.e. hydrogen, oxygen, nitrogen, phosphorus, & sulfur Yet, carbon atoms are the most predominant structures in organic molecules typically linked as carbon-to-carbon bonds All cells share a common set of carbon-containing molecules (called organic molecules ) dissolved or dispersed in H 2 0 as a common medium of housing and interaction.