AP Biology 1 Homeostasis and Evolution

Homeostasis 2 Homeostasis is the way an organism maintains a stable internal environment within itself Body systems coordinate their activities to maintain homeostasis. This is done through the use of positive and negative feedback loops These finely tune the internal workings of the organism

Remember Feedback Loops? 3 Negative Feedback Loops: organism responds to a stimulus by decreasing the occurrence of the stimulus or is opposite of the stimulus so that the “change” comes to an end and balance is restored Examples: Lac operon Shivering to raise body temperature Releasing insulin to lower blood sugar levels Animation of how lac operon works: coperon.html coperon.html

Negative Feedback Loops 4 RECEPTOR STIMULUS EFFECTOR RESPONSE Most feed back loops are

5 Positive Feedback Loops: Control mechanism in which an organism adjusts to a change in internal environment by further stimulating (propagating) the change Examples: Release of oxytocine during childbirth to accelerate the rate of contractions resulting (eventually) in birth

How Does Homeostasis Relate to Evolution? 6 We need to compare several species of organisms together to find similarities and differences within one another to answer that question…

Circulatory Systems of Fish, Amphibian, and Mammals 7 Similarities suggests the existence of a common ancestor millions of years ago All three circulatory systems are composed of blood, veins, arteries, capillaries, and a heart. The purpose of the blood in all 3 is to carry oxygen and other nutrients to locations throughout the organism. The major difference comes from the method through which the 3 systems carry out their blood flow.

Circulatory systems 8 Basic structures needed: circulatory fluid = “blood” tubes = blood vessels muscular pump = heart openclosed hemolymphblood

9 Two chamber heart Three chamber heart Four chamber heart

10 The mammal circulatory system is the “most advanced” because of its ability to maximize the amount of oxygen and nutrients in the organisms blood flow. The evolution of the chambered heart suggests the gradual fine tuning that is associated with homeostasis. As organisms moved from water to land, in order to maintain the stable internal environment, their circulatory system had to better evolve in order to efficiently regulate the oxygen and nutrients carried by the blood.

Respiratory Systems of Aquatic and Terrestrial Animals 11 Both aquatic and terrestrial animals have specialized organs to absorb oxygen from their surroundings, which travels their blood to provide oxygen throughout their whole body. Blobfish (Psychrolutes marcidus) about a 1 foot long and just floats along bottom of ocean floor..in danger of extinction

Evolution of gas exchange structures 12 Aquatic organisms external systems with lots of surface area exposed to aquatic environment moist internal respiratory tissues with lots of surface area Terrestrial

13 Evolutionary evidence suggests that life originated in oceans and eventually moved on to land. It is assumed that gills are primitive and evolved into lungs once organisms moved out of the ocean

Osmoregulation in Bacteria, Fish, Protists, Aquatic and Terrestrial Plants 14 Osmoregulation is the control of solute concentration and balance between water gain and water loss

osmoregulation 15 Prokaryotes respond via altered gene expression to changes in the osmotic environment Protists: Many have contractile vacuoles

In Fish 16 Freshwater Fish: Water will diffuse into the fish, so it excretes a very hypotonic (dilute) urine to expel all the excess water. Gills uptake lost salt.hypotonic 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.fish saltgills

Osmoregulation in Plants 17 Occurs via stomata

Nitrogenous Waste Production – Aquatic and Terrestrial 18 removes nitrogenous wastes (from breakdown of protein and nucleic acids) by filtering the blood nitrogenous waste type depends on environment

Nitrogen waste  Aquatic organisms  can afford to lose water  ammonia  most toxic  Terrestrial  need to conserve water  urea  less toxic  Terrestrial egg layers  need to conserve water  need to protect embryo in egg  uric acid  least toxic 19

One Way Digestion vs Complete Digestion 20 Digestion is the process of changing food into a form that the body can absorb and use as energy or as the raw materials to repair and build new tissue.

One Way Digestion 21 Some animals have a digestive system with only one opening which is the mouth. These include jellyfish, sea anemone, and planaria. They take in food through the mouth, digest the food and absorb digested material. Then the undigested parts are pushed back out through the mouth. This is also called an incomplete digestive system.

Complete Digestion 22 Most animals have a digestive system with two openings which are the mouth and the anus. These include worms, arthropods, chordates. Take in food through the mouth, then digest and absorb it over stages as it passes through the organs of the digestive system. The undigested material passes out of the body through the anus. More efficient. An animal does not have to be finished digesting and absorbing one meal before the animal takes in the next meal. The animal can have food in all stages of digestion.

Case Study 23 The story of Evans Monsignac and his miraculous homeostatic mechanisms! ed-for-27-days-Haiti-earthquake-survivors-amazing-story.html

Other Earthquake survival stories