# data[].attributes.body
All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.

Cell activities are affected by interactions with biotic and abiotic factors

Temperature

Organism activities are affected by interactions with biotic and abiotic factors.

Predator–prey relationships

symbiosis- mutualism, commensalism, parasitism

The stability of populations, communities and ecosystems is affected by interactions with biotic and abiotic factors.

Food chains and food webs

Continuity of homeostatic mechanisms reflects common ancestry, while changes may occur in response to different environmental conditions

Organisms have various mechanisms for obtaining nutrients and eliminating wastes.

Digestive mechanisms in animals such as food vacuoles, gastrovascular cavities, one-way digestive systems

Homeostatic control systems in species of microbes, plants and animals support common ancestry.

Excretory systems in flatworms, earthworms and vertebrates

Biological systems are affected by disruptions to their dynamic homeostasis.

Disruptions at the molecular and cellular levels affect the health of the organism.

Immunological responses to pathogens, toxins and allergens

Innate and adaptive immunity

Disruptions to ecosystems impact the dynamic homeostasis or balance of the ecosystem.

Invasive and/or eruptive species

Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis.

Plants, invertebrates and vertebrates have multiple, nonspecific immune responses.

INNATE IMMUNITY: Vertebrate immune systems have nonspecific and nonheritable defense mechanisms against pathogens.

Mammals use specific immune responses triggered by natural or artificial agents that disrupt dynamic homeostasis.

1. The mammalian immune system includes two types of specific responses: cell mediated and humoral.

2. In the cell-mediated response, cytotoxic T cells, a type of lymphocytic white blood cell, “target” intracellular pathogens when antigens are displayed on the outside of the cells.

3. In the humoral response, B cells, a type of lymphocytic white blood cell, produce antibodies against specific antigens.

4. Antigens are recognized by antibodies to the antigen.

5. Antibodies are proteins produced by B cells, and each antibody is specific to a particular antigen.

6. A second exposure to an antigen results in a more rapid and enhanced immune response.

# data[].attributes.body
Feedback Mechanisms

negative feedback mechanisms: maintains homeostasis: Sensor- sense changes in your body and send a message .

Integrating Center-
It receives messages from the sensors and decides which effector needs a signal to go out and fix the issue in the body. Effectors- They are either electrical impulses or chemicals that can stabilize the body and maintain homeostasis.
The blood pressure feedback loop has a few more components than depicted above. Stimulus
When you do something that changes blood pressure, such asstanding up, lying down, doing exercise, or rest, these stimulates are either a raise in blood pressure or a decrease.Receptor
When your blood pressure goes up or down, the receptor cells in the walls of your blood vessels can detect the changes. They send off a message to the integrating center in your brain.Integrating Center
Otherwise known as “mission control”, it gets the message from the receptors and decides what to do, either lower or raise the blood pressure. The center then sends out a messenger to the right effectors, namely your heart or your blood vessels. Effectors
These are the actual places in the body that directly control different functions. The integrating center will tell the heart to beat harder and faster or slow it down. Effectors in the blood pressure feedback loop are also the blood vessels. The messages to them will be to either constrict to raise the blood pressure or relax to lower the blood pressure.

ex. thermostat

positive feedback mechanisms: chain reactions

ex. blood clotting

Alteration in the mechanisms of feedback often results in deleterious consequences

ex. blood clotting

through behavioral and physiological mechanisms

ex. thermoregulation in humans

Taxis and Kinesis
Taxis: organisms respond to a stimulus by automatically moving directly toward or away from or at some defined angle to it
Kinesis: a movement behavior such that movement randomly  occurs given the presence of a stimulus
Positive Feedback
Positive feedback mechanisms amplify responses and processes in biological organisms, and the variable initiating the response is moved farther away from the initial set-point. The stimulus would be further activated.
Example: Childbirth
Many local regulators and hormones induce and regulate labor. First, estradiol induces oxytocin receptors in the uterus. Oxytocin in turn stimulates the uterus to contract AND the placenta to make prostaglandins. These prostaglandins stimulate MORE contractions of the  uterus which again causes MORE oxytocin to be produced and results in MORE contractions

Torpor
.a state of decreased physiological activity in an animal, usually by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. There are two types of torpor:

-Hibernation: during winter
-Estivation: during summer

Photoperiodism
- physiological response to change in the length of night and day
-  long day plants flower only if a period of continuous darkness is shorter than a critical period (summer plants)
- short day plants require a period of continuous darkness longer than a critical period in order to flower (early spring and fall plants)
- short-day plants are long-night plants, meaning that the plant measure is the length of the night
- long-day plants are short-night plants

# data[].attributes.body
Cell membranes are selectively permeable due to their structure

Membrane separates internal and external environs

fluid-mosaic model: structure-> selectively permeable

phospholipids (amphipathic), embedded proteins, cholesterol, glycoproteins and glycolipids

allows small non-polar molecules to diffuse

H20 through aquaporins

hydrophilic molecules/ions through channels

Cell walls provide a structural boundary, as well as a permeability barrier for some substances to the internal environments

plant cell walls made of cellulose ("fiber")

fungi and prokaryotes also have cell walls

Vocabulary:

Passive transport- down conc. gradient, no energy required

Facilitated diffusion- charged and polar molecules, protein

ex. glucose transport

Active transport-ATP + proteins required to establish conc. gradients

ex. Na+/K+ pump after action potential

Endocytosis- macromolecules and other stuff transported in via vesicles derived from the plasma membrane.

Exocytosis- vesicles fuse with plasma membrane to release macromolecules outside of cell

ex. neurotransmitter release

facilitate reactions by compartmentalizing rxns and increasing surface area

includes endomembrane system and membrane bound organelle

ex. ER, mitochondria, chloroplast, Golgi

Archaea and Bacteria generally lack internal membranes and organelles and have a cell wall

# data[].attributes.body
All living systems require constant input of free energy.

Life requires a highly ordered system

Constant free energy input is necessary or else death results

Living systems do not violate the second law of thermodynamics i.e. entropy always increases

Couple processes that increase entropy/decrease free energy (exergonic) with those that decrease entropy/increase free energy (endergonic)

Energy input exceeds energy lost

Energy-related pathways in biological systems are sequential and may be entered at multiple points in the pathway

Krebs cycle, glycolysis are examples

Organisms use free energy to maintain organization, grow and reproduce

Regulating Body Temperature/Metabolism: Endothermy

Reproduction and rearing of offspring require free energy beyond that used for maintenance and growth

Seasonal reproduction/hibernation in bears

Smaller organisms= higher metabolic rate and viceversa

Amount of free energy:

Excess results in stored energy/growth

Lack results in wasting away/death

Changes in free energy availability can result in changes in population size

Changes in free energy availability can result in disruptions to an ecosystem

What happens at higher trophic levels if producers are wiped out?

Organisms capture and store free energy for use in biological processes.

Autotrophs vs. Heterotrophs (capturing free energy)

Different energy-capturing processes use different types of electron acceptors such as NADP+ in photosynthesis

PHOTOSYNTHESIS:The light-dependent reactions of photosynthesis in eukaryotes involve a series of coordinated reaction pathways that capture free energy present in light to yield ATP and NADPH, which power the production of organic molecules.

Photosynthesis first evolved in prokaryotic organisms;

responsible for creating oxygenated atmosphere

foundation of eukaryotic photosynthesis.

Cellular Respiration: harvest energy from carbs

Glycolysis- break glucose into 2 net ATP + 2 pyruvate

Pyruvate oxidized to Acetyl-CoA in mitochondria

Krebs Cycle- ATP produced via substrate level phosphorylation, CO2 released, NADH/FADH2 created

During cellular respiration, a glucose molecule is gradually broken down into carbon dioxide and water. Along the way, some ATP is produced directly in the reactions that transform glucose. Much more ATP, however, is produced later in a process called oxidative phosphorylation. Oxidative phosphorylation is powered by the movement of electrons through the electron transport chain, a series of proteins embedded in the inner membrane of the mitochondrion.

Glycolysis. In glycolysis, glucose—a six-carbon sugar—undergoes a series of chemical transformations. In the end, it gets converted into two molecules of pyruvate, a three-carbon organic molecule. In these reactions, ATP is made, and +NAD​+ is converted to NADH

Pyruvate oxidation. Each pyruvate from glycolysis goes into the mitochondrial matrix—the innermost compartment of mitochondria. There, it’s converted into a two-carbon molecule bound to Coenzyme A, known as acetyl CoA. Carbon dioxide is released and NADH is generated.

Citric acid cycle. The acetyl CoA made in the last step combines with a four-carbon molecule and goes through a cycle of reactions, ultimately regenerating the four-carbon starting molecule. ATP, NADHand 2FADH​ are produced, and carbon dioxide is released.

Oxidative phosphorylation. The NADH made in other steps deposit their electrons in the electron transport chain, turning back into their "empty" forms. As electrons move down the chain, energy is released and used to pump protons out of the matrix, forming a gradient. Protons flow back into the matrix through an enzyme called ATP synthase, making ATP. At the end of the electron transport chain, oxygen accepts electrons and takes up protons to form water.

Electron Transport Chain (general)

CR: high energy electrons from NADH and FADH2 move toward the terminal electron acceptor, oxygen

PS: the terminal electron acceptor is NADP+

Proton gradient created as electrons are passed

Chemiosmosis uses proton gradient and ATP synthase to create ATP from ADP + P (oxidative phosphorylation)

ATP→ADP is exergonic and couples with many endergonic reactions/

Organisms must exchange matter with the environment to grow, reproduce and maintain organization.

Molecules and atoms from the environment are necessary to build new molecules.

C from CO2 incorporated into Glucose and Lipids

P and N needed for amino acids and nucleic acids

H2O is necessary and unique: polarity and H bonding

Cohesion and Adhesion

Surface Area to Volume Ratio

More volume means more resources
needed from environment

Therefore smaller cells necessary

# data[].attributes.body
2A: Growth, reproduction and maintenance of the organization of living systems require free energy and matter.
2B: Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments.
2C: Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis.
2D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system's environments.