Properties of Life

Cells

What makes something a cell? A cell membrane. It is the first essential feature of all cells because it separates the living material within a cell from the nonliving environment around it.

i. Cell Theory:

• all organisms are made of cells

• cells come from other cells

• cells are the basic unit of life

ii. Cell Structure:

• Unicellular- consisting of a single cell

• Multicellular- consisting of multiple cells

a. Simple: undifferentiated tissue, where all cells are in direct contact with the environment (ex.- filaments, biofilms, algae)

b. Complex: differentiated tissue, where all cells are NOT in direct contact with the environment (ex.- vascular plants, all animals)

Reproduction

i. sexual

• internal (fertilization occurs inside the body) vs external (fertilization occurs outside the body)

• Meiosis-gametes-fusion-zygote-mitosis-ontogeny(development of an organism from egg to maturity)

ii. asexual

• binary fusion: division of one cell into two identical daughter cells following the replication of DNA. Results in 2 equal sized cells.

• budding: a new organism develops from an outgrowth of the parent. The resulting offspring is smaller than the parent.

• fragmentation: a mature organism breaks into smaller fragments

iii. When is each one beneficial?

Sexual reproduction is beneficial in changing environments when new genetic material may be beneficial.

Asexual reproduction is beneficial in stable environments; it occurs more quickly, requires less energy, and can occur without a mate.

Energy Acquisition and Processing

The chemical reactions that occur in an organism require energy. Organisms require energy from 2 sources: the sun or chemical compounds.

i. Energy and Carbon source

• phototroph- use sunlight for energy and carbon from CO2

• chemoheterotroph- use organic matter for their energy and carbon source

• mixotrophs- use photosynthesis and or organic matter depending on availability. If light is present, they will photosynthesize. In the absence of light, they prey on other organisms.

ii. Metabolism- chemical reactions in cells to convert energy from one form to another and build (anabolism) or break down (catabolism) molecules. Catabolic reactions break down molecules to obtain energy and carbon building blocks. Anabolic reactions use the building of blocks to synthesize molecules that the cell uses.

• catabolic ex.- cellular respiration breaks down glucose to generate ATP.

• Anabolic ex.- creation of proteins from amino acids, and the formation of DNA strands from nucleotides.

Information (processing, storage, and decoding)

“Organisms process genetic information, respond to the environment, adjust and maintain stable internal conditions.”

i. Response- reaction of a cell, tissue, or organism to a stimulus (chemical, physical, or biological). Plant responses tend to be growth or turning responses (tropism), whereas animal responses are more directed movements (taxis). Responses can be positive, toward a stimulus, or negative, away from a stimulus.

• chemo- a chemical stimulus (bacterial cells direct their movements according to varying chemicals/pollutants in their environment; immune cells to respond to molecules released during injury; (fish move toward food)

• photo- a light stimulus

• Thigmo - a touch response

• Geo- response to the force of gravity

• Hydro- response to moisture or water

ii. Regulation and feedback loops

a. Regulation- homeostasis; maintaining a consistent or balanced internal environment. Homeostasis is important because enzymes typically function within a narrow range of conditions. Membrane permeability and structure is dependent on temperature. Essentially the body functions when internal conditions are stable.

b. Feedback Loops- homeostasis is maintained via feedback loops.

1) negative feedback loops: most homeostatic systems are based on negative feedback loops. Negative loops produce a counter- response to return the body to a stable state. Ex: osmoregulation, blood pressure and thermoregulation

2) positive feedback loops: positive loops amplify or intensify a response to produce a desired outcome. Ex: blood clotting, breastfeeding, ripening fruit

iii. Genetic info and storage

Organisms store info in DNA. Genes are the basic structural and functional unit of heredity.

Evolutionary Adaption

i. Defining evolution- a change in the heritable traits or genetic make-up of a population over time.

ii. Adaption- An inherited characteristic that increases an individuals fitness in a particular environment. Adaptions can’t be gained because of need; they are inherited and thus are already present. They can be physical, behavioral, or physiological. Adaptions can’t occur within an organisms lifetime.

• not everything is an adaptation. Some traits remain due to previous conditions, these are called vestigial traits. Some traits are by-product of the cells or tissues function. Other traits occur by chance.

iii. Fitness- reproductive success. The ability to to survive and reproduce in a given environment.