1. Effects of Disruptions
5.5: Biological systems are affected by disruptions to their dynamic homeostasis.
Effects of Disruptions

2. Homeostasis is a System Property
All levels of biological organization are able to exist at a homeostatic stability.
Anything that moves the system away from homeostasis can be considered a “disruption”.
Disruptions to homeostasis at any level of the system will affect other levels of the system as well.

3. Molecular Disruptions
Toxins: substances that interfere with specific metabolic processes or destroy cells.
Ex. Cyanide interrupts the function of cytochrome c oxidase (in the mitochondrial ETC), stopping cellular respiration.
Note: Not to scale.

4. Ex: A snake venom toxin blocks removal of acetylcholine from synapses, preventing communication between nerves and muscles.

5. Ex: Bacterial Toxins affect various cellular systems, which then affect tissues, organs, organ systems, and the organism
Image by David S. Goodsell, The Scripps Research Institute. All rights reserved.

6. Ex. Dehydration
The changes in tonicity that accompany a loss of water lead to shifts in molecular concentration that make it difficult for cellular work to continue.

7. Ecosystem Disruptions
Disruptions to ecosystems can adversely affect the balance of abiotic and biotic conditions in the ecosystem.
Ex. Invasive Species

8. Ex. Disturbance
Natural and Human disturbances cause large-scale, rapid changes to the structure of the ecosystem.

9. Restoration of Homeostasis
Biological systems are all able to use feedback mechanisms to respond to disruptions, and rebound IF the disruption is not too large and rapid for those mechanisms to function.

10. Ex. Blood Clotting
Image by David S. Goodsell, The Scripps Research Institute. All rights reserved.

11. 5.6: Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis.
Immune Systems

12. Pathogens, agents that cause disease, infect a wide range of animals, including humans
The immune system recognizes foreign bodies and responds with the production of immune cells and proteins
All animals have innate immunity, a defense active immediately upon infection
Vertebrates also have adaptive immunity
Phagocyte- a type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles
Lymphocyte- white blood cell

13. Pathogens (such as bacteria, fungi, and viruses)
Figure 43.2
Pathogens (such as bacteria, fungi, and viruses)
INNATE IMMUNITY (all animals)
Barrier defenses:
Skin Mucous membranes Secretions
Recognition of traits shared by broad ranges of pathogens, using a small set of receptors •
Internal defenses:
Phagocytic cells Natural killer cells Antimicrobial proteins Inflammatory response
• Rapid response
ADAPTIVE IMMUNITY (vertebrates only)
Humoral response:
Antibodies defend against infection in body fluids.
Recognition of traits specific to particular pathogens, using a vast array of receptors •
Cell-mediated response:
Cytotoxic cells defend against infection in body cells.
• Slower response

14. Non-specific Defenses
All organisms have non-specific defenses.
“Pattern Recognition Particles”: All organisms have receptors that recognize and respond to molecules that are present in general classes of pathogens.

15. Antibiotics
Based on defensive molecules made by bacteria and fungi (who in turn have defenses against the antibiotics…)
Image by David S. Goodsell, The Scripps Research Institute. All rights reserved.

16. Defense Responses in Plants

17. Non-specific vertebrate defenses
Vertebrates have a variety of external and internal defenses.
External: Skin, mucous, tears, sweat (lysozyme).
Internal: Inflammatory response (such as pain and swelling, is brought about by molecules released upon injury of infection)

18. Mast cell Red blood cells
Figure
Pathogen
Splinter
Macro- phage
Movement of fluid
Signaling molecules
Mast cell
Figure 43.8 Major events in a local inflammatory response.
Capillary
Phagocytosis
Red blood cells
Neutrophil

19. Mammalian Specific Immunity
Mammals have a highly developed specific immune system.
Controlled by white
blood cells called
lymphocytes
(B and T cells)
2 major divisions:
Cell-mediated.
Humoral.
B cells and T cells have receptor proteins that can bind to foreign molecules
Each individual lymphocyte is specialized to recognize a specific type of molecule

20. Specific and Non-Specific Interactions
The specific immune response is triggered when non-specific phagocytes present molecules from pathogens (“antigens”) to lymphocytes:

21. Cell-Mediated Response
Specific T-cells are developed to target specific antigens.
These T-cells trigger the destruction of those pathogens, and infected cells through cell-cell interactions.

22. Humoral Response
Specific B-cells are developed that produce and secrete antibodies that bind to specific antigens.
These antibodies bind to the antigens on pathogens and target them for destruction by T-cells, phagocytes, or prevent them from continuing their life cycle.

23. Other lymphocytes support the action of the specific response.

24. A note about HIV/AIDS HIV is the virus that causes AIDS.
It brings about the destruction of the Immune system by infecting and killing T- Helper Cells

25. Antibody Structure
T-cells and B-cells have specific receptors on their cell membranes that respond to specific antigens.

26. Somatic recombination of different segments of the B-cell and T-cell receptor genes generates many thousands of different possible antigen binding sites.

27. Clonal Selection
When lymphocytes mature, any who have receptors that react with “self” molecules are eliminated.
When lymphocytes are presented with an antigen, only those with reactive receptors are allowed to reproduce.

28. Antibody Action
Antibodies work by preventing pathogens from infecting cells, and identifying pathogens to phagocytic cells.

29. Immunological Memory
Whenever the immune system is exposed to an antigen, and a specific response is generated, a population of lymphocytes with reactive receptors will remain alive and available in the immune system for future exposure to the same antigen.
Subsequent exposures will trigger a faster and larger immune response.

30. Regulation of behavior
5.7: Timing and coordination of behavior are regulated by various mechanisms and are important in natural selection.
Regulation of behavior

31. Behavior Behavior: Anything an organism does, and how it does it.
All Organisms are able to respond to changes in the environment by changing their behavior.

32. Ex. Auxin and the phototropic response.

33. Ex. Phytochromes and the Flowering Response

34. Ex. Circadian Rhythms in Animals
Molecular Clocks in Mammals
Click image for Human CR Video

35. Ex. Hibernation Responses

36. Ex. Fruiting Body Formation

37. Ex. Quorum Sensing

38. In All Cases
Behavior is a result of interactions between the environment and the organism.
Behavior is regulatory in nature.
Any behavior with a genetic component can be adapted by natural selection.