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AP Biology Unit Four Maintaining Homeostasis

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Presentation on theme: "AP Biology Unit Four Maintaining Homeostasis"— Presentation transcript:

1 AP Biology Unit Four Maintaining Homeostasis
2/11 – 3/29

2 Just bear with me……

3 BIG IDEA 2: Biological systems utilize energy and molecular building blocks to grow, to reproduce, and to maintain homeostasis. BIG IDEA 3: Living systems store, retrieve, transmit, and respond to information essential to life processes. BIG IDEA 4: Biological systems interact, and these interactions possess complex properties.

4 We will cover….. Feedback control AGAIN!
Evolutionary development of animal organ systems to control homeostasis with the environment Cellular signaling Specific systems: endocrine, nervous, immune Plants – homeostatic`mechanisms and how they respond

5 Organism Organization
Cells Tissues Organs Organ Systems (not technically in plants) Organism The structure of a component of an organism underlies its function.

6 Homeostasis occurs in ALL organisms
Involves all levels (except unicellular organisms): cells, organs, organisms Reflects continuity and change Shaped by evolution Affected by disruptions Defenses evolved to maintain

7 Remember…. Body systems coordinate their activities to maintain homeostasis.

8 Boseman videos are helpful!


10 behavior Timing and control disruption Feedback loops response environment Shaped by evolution HOMEOSTASIS physiological abiotic biotic defenses development

11 Regulator or conformer?
Regulators – control internal fluctuations (us) Conformers – allow internal conditions to vary with environmental changes (temp in ectotherms)

12 acclimatization An animal’s normal range of homeostasis may change as the animal adjusts to external environmental changes


14 Video on Feedback Loops
As you watch, take notes on the basic diagram of a negative feedback loop What are the component parts Use two biological examples

15 Negative Feedback Loops



18 In mammals, a group of neurons in the hypothalamus functions as a thermostat
Fever as a response to infection can reset the hypothalamus set point.

19 Other circulatory adjustments: Countercurrent exchange in temp regulation
Common in marine mammals and birds the heat in the arterial blood leaving the body core is transferred to the venous blood


21 Other thermoregulatory mechanisms
Insulation Evaporative heat loss Behavioral responses Regulation of metabolic heat - endotherms use metabolic heat to maintain their body temp - ectotherm gain heat mostly from environment

22 Raising temp metabolically
Mammals and birds regulate rate of metabolic heat production through activity and shivering. Some mammals generate heat through nonshivering thermogenesis, rise in metabolic rate produces heat instead of ATP. Some mammals have brown fat for rapid heat production.

23 Negative feedback: control of sugar in the blood

24 Islets of Langerhans

25 Positive feedback: oxytocin to induce childbirth

26 Ethylene in fruit ripening
Has anyone told you to put a banana in the bag with your apples or pears to help them ripen?

27 Biological Examples of Negative Feedback Loops
Thermoregulation Blood Sugar Levels Blood volume Respiratory Rate

28 Negative Feedback Loops

29 Homeostatic mechanisms and organ systems are shaped by evolution.
Excretory systems deal with osmoregulation (water balance) and excretion of nitrogenous wastes

30 osmoregulation Prokaryotes respond via altered gene expression to changes in the osmotic environment Protists: Many have contractile vacuoles

31 Freshwater: Water will diffuse into the fish, so it excretes a very hypotonic (dilute) urine to expel all the excess water. Gills uptake lost salt. A marine fish has an internal osmotic concentration lower than that of the surrounding seawater, so it tends to lose water and gain salt. It actively excretes salt out from the gills.


33 dealing with nitrogenous wastes
The excretory system in vertebrates: - maintains water, salt, and pH balance - removes nitrogenous wastes (from breakdown of protein and nucleic acids) by filtering the blood - nitrogenous waste type depends on environment


35 Excretory system in flatworms

36 Excretory system in earthworms

37 In humans

38 The kidney works closely with the circulatory system in that the salt content, pH, and water balance of the blood is controlled by the kidneys.

39 Within the kidney, fluid and dissolved substances are filtered from the blood and pass through nephrons where some of the water and dissolved substances (nutrients) are reabsorbed. The remaining liquid (including toxins) and wastes form urine.

40 What homeostatic mechanisms work here?
Concentrated blood (too much salt, too little water) signal receptors in the hypothalamus to stimulate release of ADH (AntiDiuretic Hormone) by the pituitary gland which influences kidney to reabsorbs water, making blood more dilute.

41 Alcohol inhibits the release of ADH, causing the kidneys to produce dilute urine.

42 If, on the other hand, a person drinks an excess of water, the sodium in the blood becomes more dilute and the release of ADH is inhibited. The lack of ADH causes the nephrons to become practically impermeable to water, and little or no water is reabsorbed from them back into the blood. Consequently, the kidneys excrete more watery urine until the water concentration of the body fluids returns to normal.


44 Development of respiratory systems

45 The Respiratory System
- delivers oxygen to and removes CO2 from the circulatory system and eventually the tissues - in humans, this occurs in the alveoli of the lungs which are covered in capillaries The respiratory system works closely with the circulatory system.

46 Fish respiratory system

47 Countercurrent exchange

48 How are lungs perfected for terrestrial living?

49 lungfish

50 How does structure correlate with the function of the parts?

51 What homeostatic mechanisms are at work here?
Breathing is controlled by the medulla of the brainstem. It repeatedly triggers contraction of the diaphragm initiating inspiration. The rate of breathing changes with activity level in response to carbon dioxide levels, and to a lesser extent, oxygen levels, in the blood. Carbon dioxide lowers the pH of the blood (water and CO2 make carbonic acid H2CO3). Hemoglobin carries oxygen and also can carry bicarbonate ions (form of CO2)..

52 There are chemosensors in the carotid artery and the arch of the aorta
There are chemosensors in the carotid artery and the arch of the aorta . The sensors of the aortal are sensitive to the level of oxygen in the blood. Sensors near the medulla are sensitive to the level of carbon dioxide in the blood. If oxygen level falls or carbon dioxide levels vary too greatly from the set point, a negative feedback mechanism increases respiratory rate.


54 Mammals are most sensitive to carbon dioxide levels because the amount of CO2 varies most in respiration in response to different metabolic and environmental conditions.

55 Circulatory System Function – moving substances around: nutrients (from digestion), wastes (from excretion), O2 and CO2 (from respiration), hormones (endocrine), immune substances, and lymph fluid. Closely tied to the digestive, excretory, respiratory, endocrine, immune, and lymphatic system.

56 Types: Open – blood mixes with internal organs directly (insects, arthropods, mollusks) Closed – blood stays in vessels (earthworms, some mollusks such as octopi, vertebrates


58 Structures vary for types of animals:
Fish – one ventricle, one atrium, gill capillaries, single loop Amphibian – one v, 2 a, lung and skin capillaries, double circulation (one to body, one to lungs) Reptiles – partially divided v, 2 a, other same as amphibs Mammal, Birds – 2 v, 2 a, lung capillaries, double circulation



61 Flow of blood in Mammalian Heart:
right, right, lungs, left, left, body (right side unoxygenated traveling to lungs the pulmonary artery (arteries – away, veins – toward heart). R R lungs L L body



64 Beating of the heart controlled when cardiac muscles transfers an electrical signal via the SA (sinoatrial) node or “pacemaker” (in top right atrium) to the AV (atrioventricular) node between the right a and v.

65 Blood Pressure Force of blood against an artery. Measured as Systolic (Super Top Most….when ventricles are contracting) over Diastolic (down, minimum, when ventricles fill with blood); normal 120/80


67 How does negative feedback loops work here? For regulating heart beat
Receptor Stimulus Effector response

68 Development of Digestive Systems
Intracellular Digestion – ex amoeba Extracellular Digestion – bacteria, us

69 Digestive Systems in Animals
One opening – sac (cnidarians, flatworms) Tube – roundworms and on Why more advantageous?

70 The Digestive System in Humans
Ingestion, mechanical and chemical breakdown of food, absorption of nutrients, elimination of wastes


72 Pathway Oral Cavity – only carbs broken down here! Mechanical digestion - teeth Esophagus – just a muscular tube, peristalsis pushed food down Stomach – only protein broken down here! (low pH due to secretion of gastric juice), lots of churning in another muscular organ

73 The Big Boys…..small intestines and accessory glands
Carbs, proteins, and lipids broken down here. Most digestion and absorption here! Pancreatic enzymes and bile (for fat) from the liver via the gallbladder released in this area. Microvilli extend the surface area.

74 Microvilli in the small intestine

75 Finishing up… Large intestine (colon)- no digestion, just reabsorbs water and creates feces

76 Can you live without your…How?
Stomach? Small Intestine? Large intestine?

77 How does the homeostatic evolution of these systems reflect:
Continuity Divergence

78 Case Study The story of Darlene Etienne and her miraculous homeostatic mechanisms!

79 "We cannot really explain this because that's just (against) biological facts," Lambert told a news conference. "We are very surprised by the fact that she's alive. ... She's saying that she has been under the ground since the very beginning on the 12th of January so it may have really happened — but we cannot explain that." Authorities say it is rare for anyone to survive more than 72 hours without water, let alone 15 days. But Etienne may have had some access to water from a bathroom of the wrecked house, and rescuers said she mumbled something about having a little Coca-Cola with her in the rubble. Fuilla said Etienne did not suffer a broken leg, as first reported, but that both legs were trapped under debris. "Both legs are very sore," he said.

80 Earthquake survival stories
Rescuers said the 16-year-old, who was severely dehydrated and covered in dust, possibly survived by drinking bathwater but could not have lasted much longer. Earthquake survival stories

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