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AP Biology Big Idea #2
Transcript of AP Biology Big Idea #2
2.B: Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments.
2.C: Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis.
2.D: Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.
2.E: Many biological processes involved in growth, reproduction and dynamic homeostasis include temporal regulation and coordination. Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Growth, reproduction and maintenance of the organization of living systems require
free energy and matter. Growth, reproduction and dynamic homeostasis
require that cells create and maintain internal environments that are different from their
external environments. Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis. THE END Big Idea #2 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 All living systems require
constant input of free energy. 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.
Don't worry too much about the Calvin Cycle as long as you know the output
Photosynthesis first evolved in prokaryotic organisms;
responsible for creating oxygenated atmosphere
foundation of eukaryotic photosynthesis. Organisms capture and store
free energy for use in biological processes 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
Too the Electron Transport Chain!
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 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 Growth and dynamic homeostasis
are maintained by the constant movement
of molecules across membranes 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 Eukaryotic cells maintain internal
membranes that partition the cell
into specialized regions 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 Organisms use feedback mechanisms
to maintain their internal environments and respond to external environmental changes negative feedback mechanisms: thermostat ex.
ex. trp operon
positive feedback mechanisms: amplified response
ex. blood clotting
Alteration in the mechanisms of feedback often results in deleterious consequences
ex. blood clotting continued! Organisms respond to changes in their external environments through behavioral and physiological mechanisms
EX. thermoregulation in humans Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment. Homeostatic mechanisms reflect both
common ancestry and divergence due to adaptation in different environments 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
Organism activities are affected by interactions with biotic and abiotic factors.
symbiosis- mutalism, 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. Many biological processes involved in growth, reproduction and dynamic homeostasis include temporal regulation and coordination. Timing and coordination of specific events
are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms. Observable cell differentiation results from the expression of genes for tissue-specific proteins.
Induction of transcription factors during development results in sequential gene expression.
Genetic mutations can result in abnormal development.
Programmed cell death (apoptosis) plays a role in the normal development and differentiation.
Morphogenesis of fingers and toes Timing and coordination of physiological
events are regulated by multiple mechanisms. In plants, physiological events involve interactions between environmental stimuli and internal molecular signals.
Phototropism, or the response to the presence of lightPhotoperiodism, or the response to change in length of the night, that results in flowering in long-day and short-day plants
In animals, internal and external signals regulate a variety of physiological responses that synchronize with environmental cycles and cues.
Circadian rhythms, or the physiological cycle of about 24 hours that is present in all eukaryotes and persists even in the absence of external cues Timing and coordination of behavior are
regulated by various mechanisms and are
important in natural selection. Individuals can act on information and communicate it to others.
innate (inherited) vs. learned behavior
Responses to, and communication of information are vital to natural selection
1. In phototropism in plants, changes in the light source lead to differential growth, resulting in maximum exposure of leaves to light for photosynthesis.
2. In photoperiodism in plants, changes in the length of night regulate flowering and preparation for winter.
3. Behaviors in animals are triggered by environmental cues and are vital to reproduction, natural selection and survival.
4. Cooperative behavior within or between populations contributes to the survival of the populations. (mutualism)