The Nature of Life: Matter, Energy, and Entropy

1. Choose to view chapter section with a click on the section heading. • The Nature of Life • How Matter and Energy Enter Living Systems • The Ocean’s Primary Productivity • Energy Flow Through the Biosphere Chapter Topic Menu

2. The Nature of Life The Nature of Life Chapter 4 Pages 4-2 to 4-6

3. The Nature of Life Theoretical physicist Stephen Hawking: “The laws of science do not distinguish between the past and the future. In order to survive, human beings have to consume food which is an ordered form of energy, and convert it into heat, which is a disordered form of energy… The progress of the human race in understanding the universe has established a small corner of order in an increasingly disordered universe.” • This principle of physics called entropy, or randomness, appears to be the driving force of all life in our universe. The Nature of Life Chapter 4 Pages 4-2 to 4-6

4. The Nature of Life • Defining life appears simple if you compare a fish and a rock. From a scientific point of view, it’s not quite so cut-and-dried. Often life and nonlife share the same elements; matter, carbon atoms and energy reactions. • Energy reactions found in living systems also exist outside of life. For example: fire results when a reaction releases chemicalenergy within substances. Living systems use energy similarly– by releasing chemical energy for life processes. • All life uses energy. Therefore it is possible to define “life” based on the characteristics living systems have apart from nonliving systems with respect to energy use. The Nature of Life Chapter 4 Pages 4-2 to 4-6

5. Matter and Energy • Life requires matter and energy to exist. All living organisms are composed of about 13 of 118 known elements from the periodic table. • Carbon, hydrogen, oxygen, and nitrogen account for 99% of the mass. Ten other elements account for the remaining 1%. These elements, in combinations, account for all biological chemicals. The Nature of Life Chapter 4 Pages 4-3 to 4-5

6. Matter and Energy Elements Essential for Life The Nature of Life Chapter 4 Pages 4-3 to 4-5

7. Matter and Energy • Elements, in various combinations, account for all biological chemicals. • These range from very simple sugars to DNA – the most complex known molecule. • Scientists recognize more than 1.6 million different species. Some biologists estimate that as many as 30 million may exist. • All organisms organize matter into biological chemicals and into cells. A cell is the smallest whole structure that can be defined as a living system. Some organisms consist of single cells; others consist of billions of codependent cells. Non-living things consists of matter, but don’t consist of cells. The Nature of Life Chapter 4 Pages 4-3 to 4-5

8. Matter and Energy • The first way fire differs from life: Fire consists of matter (gases), but it doesn’t consist of cells. It lacks any other structure that organizes matter in the way that living systems do. The Nature of Life Chapter 4 Pages 4-3 to 4-5

9. Matter and Energy • Energy is defined as the capacity to do work; it’s necessary for life because living systems use it to accomplish the processes of life: reproduction, growth, movement, eating, etc. • Organisms need energy to break down complex molecules into simple molecules, and to build distinct complex molecules from simple molecules. The Nature of Life Chapter 4 Pages 4-3 to 4-5

10. Matter and Energy • The first law of thermodynamics states that energy cannot be created or destroyed only transferred from one state to another. • Although organisms require energy, they cannot create it; all living systems acquire energy from outside sources. The Nature of Life Chapter 4 Pages 4-3 to 4-5

11. Matter and Energy The Nature of Life Chapter 4 Pages 4-3 to 4-5 What’s a “machine?”

12. Matter and Energy • A machine is a combination of matter capable of using energy to perform useful work. • Arguably living systems are machines. They’re combinations of matter capable of using energy to perform useful work. • What separates living systems from other machines is that they’re the only machines known that were not created by human beings. • Machines are also incapable of reproducing themselves (at least so far). • Organisms use energy for the useful work of the processes of life, including creating organization. The Nature of Life Chapter 4 Pages 4-3 to 4-5

13. Matter and Energy • The second way fire differs from living things: A fire results from the release of energy, but it is not performing useful work in the sense that it doesn’t regulate energy use or matter acquisition to meet its needs. It simply burns the available fuel. • A living system uses energy for the processes of life, including creating the organization that fire lacks. The Nature of Life Chapter 4 Pages 4-3 to 4-5

14. Entropy • The second law of thermodynamics states that disorder increases with the passage of time. • It is the law that random processes lead to chaos and simplicity, not order and sophistication. In other words, it says that the universe is “wearing out,” or moving toward a state of disorganization. • This explains why energy is useful—it flows from areas of high concentration to low concentration; and it is this flow that living systems can harness to perform useful work. The Nature of Life Chapter 4 Pages 4-5 to 4-6

15. Entropy • Whenever you use energy, taking it from one form to another to perform work, some energy is lost as heat (another form of energy). • Eventually all energy and matter will be distributed evenly throughout the universe, but the distribution process isn’t uniform as it progresses. • There are areas with high order and others with low order. The Nature of Life Chapter 4 Pages 4-5 to 4-6

16. Entropy • Entropy is the measure of how much unavailable energy exists in a system due to even distribution. High entropy = low organization and low energy potential. • Living systems use energy to create order and to gather and store potential energy. The increased order is local and temporary, and requires more energy to create than it retains. Here, matter exists in a low-entropy (organized) state. • Example: About 85% of the energy required to organizeprotein into complex muscletissue is ultimately lost as heat in creating the tissue. The Nature of Life Chapter 4 Pages 4-5 to 4-6

17. How Matter and EnergyEnter Living Systems How Matter and Energy Enter Living Systems Chapter 4 Pages 4-7 to 4-12

18. Autotrophy and Heterotrophy • All living things obtain the matter and energy they need from external sources. • Terrestrial organisms and most marine organisms get their energy directly or indirectly from the sun. • Energy in the form of sunlight combines with inorganic compounds to become energy-rich organic compounds. These compounds provide energy when living systems break them down during respiration. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-7

19. Autotrophy and Heterotrophy • Autotrophy is the process of self-feeding – the ability to create their own carbohydrates. Plants are autotrophs. • Autotrophs can feed themselves by converting the energy from sunlight and inorganic compounds into carbohydrates. • Organisms, like humans, that cannot produce their own carbohydrates must consume other organisms to get it, and are called heterotrophs. • All heterotrophs rely on photosynthesizing plants, bacteria and other microorganisms for life either directly or indirectly by consuming other organisms. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-7

20. Cellular Respiration • Organisms that use oxygen engage in cellular respiration, a process that releases energy from carbohydrates to perform the functions of life. (Note that this differs from respiration as commonly used to mean breathing). • The chemical process is represented by the formula: • Sugar (glucose, a simple carbohydrate) plus oxygen converts to carbon dioxide, water and energy. • This conversion of the food you eat into energy your body uses is why you need oxygen to live, and why you exhale carbon dioxide. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-7 to 4-8

21. Photosynthesis • Primary producers are organisms that combine energy from sunlight with inorganic materials to form energy-rich organic compounds. • They are the conduit through which the biosphere gets almost all its energy. • Primary producers harness only about one two-thousandth of the light reaching Earth, yet this powers life. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

22. Photosynthesis • Organisms with chlorophyll account for the vast majority of primary producers (plants, certain bacteria and other microorganisms). • It allows these organisms to capture sunlight energy to produce carbohydrates from inorganic material. • Carbohydrates are high-energy compounds living systems use as food. • Simple carbohydrates are sugars (saccharides) like glucose. • Complex carbohydrates are long sugar chains called polysaccharides, commonly called starches. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

23. Photosynthesis • The process of using light energy to create carbohydrates from inorganic compounds is called photosynthesis. • Carbohydrates consist of carbon, hydrogen and oxygen. • During photosynthesis, organisms use light energy to disassemble carbon dioxide and water molecules, rebuilding them into carbohydrates. • Because the carbon dioxide and water have more oxygen than is needed to make carbohydrate, the process also releases oxygen needed for respiration. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

24. Photosynthesis • Note that photosynthesis is a complimentary process to respiration. The formula representing photosynthesis is: • During photosynthesis autotrophs use carbon dioxide, water and sun energy to create high-energy carbohydrates. • During respiration, they consume oxygen and release low energy carbon dioxide. • Through photosynthesis and respiration, carbon, oxygen and water recycle continuously from inorganic to organic form and back. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

25. Photosynthesis • Respiration as described above is aerobic respiration, meaning respiration that uses oxygen. • Some organisms exist in environments without oxygen through anaerobic respiration. • Anaerobic respiration is the process of releasing energy for the processes of life through chemical reactions that do not require oxygen. • Anaerobic respiration is not as efficient as aerobic respiration. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

26. Photosynthesis Energy Transfer How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

27. Photosynthesis EnergyCycle How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

28. Photosynthesis EnergyCycle How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

29. Photosynthesis • Without primary production – the photosynthesis in plants, bacteria, and other microorganisms all over the world – you would not have the oxygen you need for respiration. • You would also not have the carbohydrates you need for energy. • Humans and all heterotrophs reply on photosynthesizing plants, bacteria and other microorganisms for life. • This is why the health of natural environments is a crucial issue. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-9 to 4-11

30. Chemosynthesis • Not all the energy used by living systems use comes directly or indirectly from the sun; there is another process called chemosynthesis. • Chemosynthesis is the process of using chemicals to create energy-rich organic compounds. • This is similar to photosynthesis because it produces carbohydrates. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-11 to 4-12

31. Chemosynthesis • Chemosynthetic organisms are also primary producers. • Both chemosynthesis and photosynthesis are forms of fixation. Fixation is the process of converting or fixing an inorganic compound into a useable organic compound. • Chemosynthesis and photosynthesis both fix carbon into carbohydrates. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-11 to 4-12

32. Chemosynthesis • Instead of light energy, chemosynthesis uses chemical energy within inorganic compounds. • It’s not as efficient as photosynthesis, and produces waste products other than oxygen. • Although the existence of chemosynthesis has been known for some time, hydrothermal vent communities weren’t discovered until 1977 by Woods Hole Oceanographic Institute scientists, diving in the submersible Alvin. • These communities live well below the reach of sunlight and rely on chemical energy from the minerals in the hot spring water. • There are also “cold seep” chemosynthetic communities, where primitive single cell organisms use methane that seeps from the sea bottom. How Matter and Energy Enter Living Systems Chapter 4 Pages 4-11 to 4-12

33. The Ocean’s Primary Productivity The Ocean’s Primary Productivity Chapter 4 Pages 4-13 to 4-22

34. Marine Biomass • The main “products” of primary production are carbohydrates. • Carbohydrates are the primary units of useable energy in living systems, plus a source of carbon used in an organism’s tissues. • Scientists measure primary productivity in terms of the carbon fixed (bound) into organic material. • This is expressed as grams of carbon per square meter of surface area per year (gC/m2/yr). • Current estimates are that the oceans’ primary average productivity ranges from 75 to 150 gC/m2/yr. • The estimates for land and marine primary productivity put land’s slightly higher at 50 to 70 billion metric tons of carbon annually versus 35 to 50 billion. The Ocean’s Primary Productivity Chapter 4 Pages 4-13 to 4-15

35. Marine Biomass • Biomass is the mass of living tissue, while the biomass at a given time is called the standing crop (both express both terms in mass). • Marine and terrestrial systems differ with respect to the biomass of the primary producers. • The standing crop in the ocean is one to two billion metric tons, versus on land, where it’s 600 to 1,000 billion metric tons. The Ocean’s Primary Productivity Chapter 4 Pages 4-13 to 4-15 Phytoplanktonaccounts for between 92% and 96% of the ocean’s primary productivity.

36. Marine Biomass • While there is a huge difference in average standing crop between the ocean and land, their respective productivity is nearly equal. • This occurs because marine ecosystems cycle energy and nutrients much faster than on land. • The rate of photosynthesis-respiration cycle is called turnover, and the marine turnover is much shorter than terrestrial. • The shorter the turnover time, the faster the standing crop passes energy into the ecosystem. The Ocean’s Primary Productivity Chapter 4 Pages 4-13 to 4-15

37. Marine Biomass ProductivityTerrestrial and Marine The Ocean’s Primary Productivity Chapter 4 Pages 4-13 to 4-15

38. Marine Biomass • Gross primary productivity is the measure of how much energy primary producers capture for creating carbohydrates. • The primary producers use some of the energy for life processes and convert the rest into biomass (tissue and other organic material). • Gross productivity minus what’s used by the primary producers themselves is called net primary productivity. The Ocean’s Primary Productivity Chapter 4 Pages 4-13 to 4-15

39. Marine Biomass The Ocean’s Primary Productivity Chapter 4 Pages 4-13 to 4-15 Comparison of net primary productivity in marine and land-based ecosystems.

40. Plankton • Plankton are organisms that: • Drift or swim weakly in the ocean; they are at the mercy of currents, tides and other water motion. • Don’t represent any specific kind of organism, but a group of organisms with a common lifestyle and habitat. • It’s important to know that plankton are not a species, but include many species from virtually every major group of organisms found in the sea. The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18 Capturing PlanktonWith Nets.

41. Plankton • Plankton includes autotrophs and heterotrophs, as well as predators and grazers. • Most plankton are very small, but some may grow several meters long. The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18 Microscopic Photoof Plankton

42. Plankton • Some organisms start life as planktonic larvae, and then leave the plankton community as they grow large enough to swim as nektonic organisms or attach themselves to the bottom as benthic organisms. • Phytoplankton are the primary producers (autotrophs). • Zooplankton are primary and secondary consumers that feed on phytoplankton and other heterotrophic plankton. • Phytoplankton are the most important primary producers in the sea, responsible for between 92 and 96 percent of the oceans’ primary productivity. • Marine plants, kelp and other multicellular photosynthesizing organisms account for only two to five percent, with the remainder from deep ocean chemosynthesis (which may be much higher than current estimates). The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18

43. Plankton - Diatoms • Diatoms are the most dominant and productive of the phytoplankton. • Diatoms are photosynthetic organisms characterized by a rigid cell wall made of silica. • This cell wall, called a frustule, admits light much like glass, an ideal cell material for a photosynthesizer. • Diatoms are the most efficient photosynthesizers known (they can convert more than half the light energy they absorb into carbohydrate chemical energy). • There are thousands of known species, including bottom dwelling (benthic) species as well as plankton (pelagic) species. The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18

44. Plankton - Diatoms The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18

45. Plankton - Dinoflagellates • Dinoflagellates are the second most abundant phytoplankton. • Dinoflagellates are (in most species) characterized by one or two whip-like flagella, which they move to change orientation or to swim vertically in the water. • Most, but not all species of dinoflagellates are autotrophs. • Besides planktonic species, other dinoflagellate species live within coral polyps, and are the most significant primary producers in the coral reef community. • Because they can reproduce rapidly, dinoflagellates are the principal organisms responsible for plankton blooms. The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18

46. Plankton - Coccolithophores • Coccolithophores are single celled autotrophs characterized by shells of calcium carbonate (the shells are called coccoliths). • Coccolithophores live in brightly lit, shallow water. • It’s hypothesized their translucent coccoliths protect them by screening the light. • Areas with high coccolithophore concentrations may appear milky or chalky. The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18

47. Plankton - Picoplankton • Microbial plankton ecology: • Each liter of seawater contains billions of marine bacteria, archae and viruses. Although microscopic, the total mass of the bacteria alone is thought to exceed the combined mass of zooplankton and fishes. • Tropical regions were once thought to be unproductive. Picoplankton – extremely tiny plankton between .2 and 2 micrometers – may account for 79% of the photosynthesis in tropical waters and other marine habitats. The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18

48. Plankton - Picoplankton • Microbial plankton ecology. • Many picoplankton are cyanobacteria, which are bacteria with chlorophyll. These are the most common bacteria in the ocean. • Picoplankton productivity is unproductive in the sense that they’re too small for consumption by larger consumers. Heterotrophic bacteria consume them and return the nutrients to inorganic form, so picoplankton don’t contribute much to food webs. However, they play a significant role in producing oxygen, taking up carbon dioxide and producing nitrogen compounds. The Ocean’s Primary Productivity Chapter 4 Pages 4-15 to 4-18

49. Limits on Marine Primary Productivity • Limiting factors are physiological or biological necessities that restrict survival. Too much or too little of a limiting factor will reduce population. • Most autotrophs require water, carbon dioxide, inorganic nutrients and sunlight. • In the ocean, water and carbon dioxide are almost never limiting factors - inorganic nutrients such as nitrogen and phosphorous compounds can be. • Sunlight is often a limiting factor in the sea due to season, depth or water clarity. • Several factors can limit the availability of inorganic nutrients. The Ocean’s Primary Productivity Chapter 4 Pages 4-18 to 4-21

50. Limits on Marine Primary Productivity • Plankton blooms can deplete the nutrients by rapid consumption, whereby depriving other species. • In extreme cases, plankton blooms can consume all the oxygen and release by-products that are toxic in such amounts that fish and other organisms cannot survive (HABs – Harmful Algal Blooms, sometimes called “red tide”). • Plankton blooms occur naturally, but they may also be caused when pollution eliminates a limiting factor. • Nutrient-rich pollution removes nutrients as a limiting factor, allowing the plankton to overpopulate. The Ocean’s Primary Productivity Chapter 4 Pages 4-18 to 4-21