Enduring Understanding 2.D Growth and dynamic homeostasis of a biological system

1. BIG IDEA IIBiological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring Understanding 2.D Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment. Essential Knowledge 2.D.1 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.

2. Essential Knowledge 2.D.1: 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. • Learning Objectives: • (2.22) The student is able to refine scientific models and questions about the effect of complex biotic and abiotic interactions on all biological systems, from cells and organisms to populations, communities and ecosystems. • (2.23) The student is able to design a plan for collecting data to show that all biological systems (cells, organisms, populations, communities and ecosystems) are affected by complex biotic and abiotic interactions. • (2.24) The student is able to analyze data to identify possible patterns and relationships between a biotic or abiotic factor and a biological system (cells, organisms, populations, communities and ecosystems).

3. Cell activities are affected by interactions with biotic and abiotic factors. • Illustrative examples of biotic factors include: • Cell density • Biofilms • Illustrative examples of abiotic factors include: • Temperature • Water availability • Sunlight

4. Cell Density • In addition to many internal chemical factors, studies using animal cells in culture have led to the identification of many external factors, both chemical and physical, that can influence cell division and therefore control cell density. • Contact cell cycle control mechanisms include density-dependent inhibition and anchorage dependence. • In density-dependent inhibition, crowded cells stop dividing. • Anchorage dependence is a phenomenon in which cells must be attached to a substratum (i.e. extracellular matrix of a tissue) in order to divide.

5. Fig. 12-19 Anchorage dependence Density-dependent inhibition Density-dependent inhibition 25 µm 25 µm (a) Normal mammalian cells (b) Cancer cells

6. Biofilms • Metabolic cooperation between different prokaryotic species often occurs in surface-coating colonies known as biofilms. • Cells in a biofilm secrete signaling molecules that recruit nearby cells, causing the colonies to grow. • The cells also produce proteins that stick the cells to the substrate and to one another. • Channels in the biofilm allow nutrients to reach cells in the interior and wastes to be expelled.

7. Fig. 11-3 Individual rod- shaped cells 1 2 Aggregation in process 0.5 mm Spore-forming structure (fruiting body) 3 Fruiting bodies

8. Organism activities are affected by interactions with biotic and abiotic factors. • Illustrative examples of biotic factors include: • Symbiosis • Predator-prey relationships • Illustrative examples of abiotic factors include: • Water/nutrient availability • Temperature • Salinity • pH

9. Symbiosis • Symbiosis is a relationship where two or more species live in direct and intimate contact with one another. • Parasitism • Mutualism • Commensalism

10. Fig. 54-UN2

11. Predator-Prey Relationships Predation is a type of density-dependent population control whereby there is a biological interaction where a predator (an animal that is hunting) feeds on its prey (the animal that is attacked).

12. Fig. 53-19 2,500 50 Wolves Moose 2,000 40 30 1,500 Number of wolves Number of moose 20 1,000 10 500 0 0 1955 1965 1975 1985 1995 2005 Year

13. The stability of populations, communities and ecosystems is affected by interactions with biotic and abiotic factors. • Illustrative examples of biotic factors include: • Food chains & food webs • Species diversity • Population density • Algal blooms • Illustrative examples of abiotic factors include: • Water & nutrient availability

14. Food Chains & Food Webs • Trophic structure is the feeding relationships between organisms in a community – it is a key factor in community dynamics. • Food chains link trophic levels from producers to top carnivores. • A food web is a branching food chain with complex trophic interactions.

15. Fig. 54-11 Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain

16. Fig. 54-12 Humans Smaller toothed whales Sperm whales Baleen whales Elephant seals Leopard seals Crab-eater seals Squids Fishes Birds Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton

17. Limits on Food Chain Length • Each food chain in a food web is usually only a few links long • Two hypotheses attempt to explain food chain length: the energetic hypothesis and the dynamic stability hypothesis • The energetic hypothesis suggests that length is limited by inefficient energy transfer • The dynamic stability hypothesis proposes that long food chains are less stable than short ones • Most data support the energetic hypothesis

18. Limits on Food Chain Length: Energetic Hypothesis

19. Limits on Food Chain Length: Dynamic Stability Hypothesis

20. Species Diversity • Species diversity of a community is the variety of organisms that make up the community • It has two components: species richness and relative abundance • Species richness is the total number of different species in the community • Relative abundance is the proportion each species represents of the total individuals in the community

21. Fig. 54-9 A B C D Community 1 Community 2 A: 80% B: 5% C: 5% D: 10% A: 25% B: 25% C: 25% D: 25%

22. Species Diversity & Ecosystem Stability • There is growing evidence that the functioning of ecosystems is linked to biodiversity. Species play essential roles in ecosystems, so local and global species losses could threaten the stability of the ecosystem. • There is currently great concern about the stability of both natural and human-managed ecosystems, particularly given the myriad global changes already occurring. • Stability can be defined in several ways, but the most intuitive definition of a stable system is one having low variability (i.e., little deviation from its average state) despite shifting environmental conditions. • Resilience is a somewhat different aspect of stability indicating the ability of an ecosystem to return to its original state following a disturbance or other perturbation. • Diverse ecosystems are more likely to return to a state of stability following a disturbance than less diverse systems.

23. Population Density

24. Algal Blooms

25. BIG IDEA IIBiological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring Understanding 2.D Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment. Essential Knowledge 2.D.2 Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments.

26. Essential Knowledge 2.D.2: Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. • Learning Objectives: • (2.25) The student can construct explanations based on scientific evidence that homeostatic mechanisms reflect continuity due to common ancestry and/or divergence due to adaptation in different environments. • (2.26) The student is able to analyze data to identify phylogenetic patterns or relationships, showing that homeostatic mechanisms reflect both continuity due to common ancestry and change due to evolution in different environments. • (2.27) The student is able to connect differences in the environment with the evolution of homeostatic mechanisms.

27. Continuity of homeostatic mechanisms reflects common ancestry, while changes may occur in response to different environmental conditions. • Structural and functional evidence supports the relatedness of all domains and the evolution of all organisms. This evidence can be seen in the following mechanisms: • Organisms have various mechanisms for obtaining nutrients and eliminating wastes (divergence). • Homeostatic control systems in species of microbes, plants and animals support common ancestry (relatedness).

28. Organisms have various mechanisms for obtaining nutrients and eliminating wastes. • Illustrative examples include: • Gas exchange in aquatic and terrestrial plants. • Digestive mechanisms in animals such as food vacuoles, gastrovascular cavities, one-way digestive systems. • Respiratory systems of aquatic and terrestrial animals. • Nitrogenous waste production and elimination in aquatic and terrestrial animals.

29. Gas Exchange in Aquatic v. Terrestrial Plants In terrestrial plants, guard cells control the opening and closing of stomata in terrestrial plants. In aquatic plants, diffusion of O2 & CO2 occurs across thin membranes in leaves of aquatic plants.

30. Osmoregulation and Excretion • Osmoregulation is the process by which animals control solute concentrations and balance water gain and loss. • It is based largely on controlled movement of solutes between internal fluids and the external environment. • Excretion gets rid of metabolic wastes. • Most metabolic wastes must be excreted from the body. One of the most important types is nitrogenous wastes from the breakdown of proteins and nucleic acids.

31. Nucleic acids Proteins Nitrogenous bases Amino acids –NH2 Amino groups Many reptiles (including birds), insects, land snails Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes O H C N C HN C O NH2 C C C O N N O NH3 NH2 H H Ammonia Urea Uric acid Nitrogenous Waste Production & Elimination in Aquatic v. Terrestrial Animals • An animal’s nitrogenous wastes reflect its phylogeny and habitat. • The type and quantity of an animal’s waste products may have a large impact on its water balance. • Among the most important wastes are the nitrogenous breakdown products of proteins and nucleic acids. Figure 44.8

32. Forms of Nitrogenous Wastes • Animals that excrete nitrogenous wastes as ammonianeed access to lots of water: • Ammonia is released across the whole body surface or through the gills. • The liver of mammals and most adult amphibians converts ammonia to less toxic urea which is carried to the kidneys in a concentrated form: • Urea is excreted with a minimal loss of water. • Insects, land snails, and many reptiles, including birds excrete uric acid as their major nitrogenous waste: • Uric acid is largely insoluble in water and can be secreted as a paste with little water loss.

33. Homeostatic control systems in species of microbes, plants and animals support common ancestry. • Illustrative examples include: • Excretory systems in flatworms, earthworms and vertebrates. • Osmoregulation in bacteria, fish and protists. • Osmoregulation in aquatic and terrestrial plants. • Circulatory systems in fish, amphibians and mammals. • Thermoregulation in aquatic and terrestrial animals (countercurrent exchange mechanisms).

34. Excretory Systems in Flatworms, Earthworms and Vertebrates

35. Nucleus of cap cell Cilia Interstitial fluid filters through membrane where cap cell and tubule cell interdigitate (interlock) Tubule cell Flame bulb Protonephridia (tubules) Tubule Nephridiopore in body wall Protonephridia: Flame-Bulb Systems in Flatworms • The protonephridia of flatworms form a network of dead-end tubules connected to external openings. These tubules branch throughout the body. • Specialized cells called flame bulbs containing cilia cap the branches of each protonephridium. • During filtration, beating of the cilia draws water and solutes from the interstitial fluid through the flame bulb, releasing filtrate into the tubule network. • The urine excreted by freshwater flatworms has a low solute concentration, helping to balance osmotic uptake of water from the environment. Figure 44.10

36. Coelom Capillary network Bladder Collecting tubule Nephridio- pore Metanephridia Nephrostome Metanephridia in Earthworms • Most annelids have metanephridia, excretory organs that open internally to the coelom and are enveloped by a capillary network. • As the cilia beat, fluid is drawn into a collecting tubule, which includes a storage bladder that opens to the outside. • The metanephridia of an earthworm have both excretory and osmoregulatory functions. • Earthworms inhabit damp soil and usually experience a net uptake of water by osmosis through their skin. • Their metanephridia balance the water influx by producing urine that is dilute (hypoosmotic to body fluids). Figure 44.11

37. Vertebrate Kidneys • Kidneys are the excretory organs of vertebrates – they function in both excretion and osmoregulation. • Nephrons and associated blood vessels are the functional unit of the mammalian kidney. • The mammalian excretory system centers on paired kidneys which are also the principal site of water balance and salt regulation.

38. Distal tubule Proximal tubule 4 1 NaCl Nutrients H2O HCO3 H2O K+ NaCl HCO3 H+ K+ H+ NH3 CORTEX Thick segment of ascending limb Descending limb of loop of Henle 2 3 Filtrate H2O Salts (NaCl and others) HCO3– H+ Urea Glucose; amino acids Some drugs NaCl H2O OUTER MEDULLA NaCl Thin segment of ascending limb Collecting duct 3 5 Key Urea NaCl H2O Active transport Passive transport INNER MEDULLA From Blood Filtrate to Urine: A Closer Look • Filtrate becomes urine as it flows through the mammalian nephron and collecting duct – there are 5 main steps in the transformation of blood filtrate to urine. Figure 44.14

39. Adaptations of the Vertebrate Kidney to Diverse Environments • Vertebrate animals occupy a wide variety of habitats, and variations in nephron structure and function equip the kidneys of different vertebrates for osmoregulation in their various habitats. • Desert Mammals: nephron structure allows them to rid the body of slats and nitrogenous wastes without squandering water (secrete hyperosmotic/highly concentrated urine). • Aquatic Mammals: have a much lower ability to concentrate urine because dehydration is not a challenge. • Birds & Reptiles: nephrons specialized for conserving water so urine is generally highly concentrated. • Freshwater Fishes/Amphibians: secrete large amounts of very dilute urine to excrete excess water continuously. • Marine Fishes: filtration rates are low and very little urine is excreted.

40. Gill capillaries Lung and skin capillaries Lung capillaries Lung capillaries AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS FISHES Right systemicaorta Pulmonarycircuit Artery Pulmocutaneouscircuit Pulmonarycircuit Gillcirculation Heart:ventricle (V) Left Systemicaorta A A A A A A Atrium (A) V V V V V Left Right Left Left Right Right Systemiccirculation Systemic circuit Systemic circuit Vein Systemic capillaries Systemic capillaries Systemic capillaries Systemic capillaries Figure 42.4 Circulatory Systems in Fish, Amphibians and Mammals

41. Thermoregulation in Aquatic & Terrestrial Animals • Thermoregulation is the process by which animals maintain an internal temperature within a tolerable range. • Each animal species has an optimal temperature range, and thermoregulation helps keep body temperature within that optimal range. • Endotherms: warmed mostly by heat generated by metabolism. • Ectotherms: gain most of their heat from external sources.

42. Variation in Body Temperature • Animals can have either a variable or a constant body temperature. • Poikilotherm: an animal whose body temperature varies with its environment. • Homeotherm: an animal with a relatively constant body temperature. • Note: the terms “cold-blooded” and “warm-blooded” are misleading and have been dropped from the scientific vocabulary!

43. Balancing Heat Loss and Gain

44. Balancing Heat Loss & Gain • Integumentary System: skin, hair, and nails all provide mechanisms to prevent heat loss and/or gain. • Insulation: reduces flow of heat between animals and their environment. • Evaporative Heat Loss: water absorbs considerable heat when it evaporates; this heat is carried away from the body surface with the water vapor. • Behavioral Responses: sun basking, huddling, fanning wings, etc.

45. Countercurrent Heat Exchangers

46. Control of Body Temperature – Negative Feedback

47. BIG IDEA IIBiological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring Understanding 2.D Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment. Essential Knowledge 2.D.3 Biological systems are affected by disruptions to their dynamic homeostasis.

48. Essential Knowledge 2.D.3: Biological systems are affected by disruptions to their dynamic homeostasis. • Learning Objectives: • (2.28) The student is able to use representations or models to analyze quantitatively and qualitatively the effects of disruptions to dynamic homeostasis in biological systems.

49. Disruptions at the molecular and cellular levels affect the health of the organism. • Illustrative Example: dehydration/desiccation. • Dehydration is theexcessive loss of body water, with an accompanying disruption of metabolic processes. Extreme dehydration, or desiccation, is fatal for most animals. • Symptoms may include headaches, decreased blood pressure, and dizziness or fainting when standing up due to orthostatic hypotension. Untreated dehydration generally results in delirium, unconsciousness, swelling of the tongue and, in extreme cases, death. • The symptoms become increasingly severe with greater water loss. One's heart and respiration rates begin to increase to compensate for decreased plasma volume and blood pressure, while body temperature may rise because of decreased sweating. • At around 5% to 6% water loss, one may become groggy or sleepy, experience headaches or nausea, and may feel tingling in one's limbs. • With 10% to 15% fluid loss, muscles may become spastic, skin may shrivel and wrinkle (decreased skin turgor), vision may dim, urination will be greatly reduced and may become painful, and delirium may begin. Losses greater than 15% are usually fatal.

50. Disruptions to ecosystems impact the dynamic homeostasis or balance of the ecosystem. • Illustrative Example: invasive species.