EOSC 112 Lecture 5: Biosphere lecture notes

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University of British Columbia
Earth and Ocean Sciences
EOSC 112
Debeare Bart

Biosphere Learning Objectives: 1. List the environmental conditions needed to sustain life 2. Contrast the different types of living organisms based on their cellular structure and the way they acquire energy and nutrients 3. Classify marine organisms based on their habitat and lifestyle. WHY DO WE NEED C, N, P, H2O? Carbon, Nitrogen, Phosphate and Water are all essential nutrients for all living cells on the planet, they are the building blocks of the cells such as proteins and lipids, etc. but they are needed to build the DNA itself. Living organisms need two things – a source of energy and a source of raw materials to build living tissues and skeletons or shells. Life on Earth is water based, but in addition to this, organisms need a wide range of other elements. Besides carbon and water – the top two are nitrogen and phosphorus. - Nitrogen is needed to produce proteins - Phosphorus is a major constituent of DNA. Other elements are essential – but in trace amounts. Many metals for example are constituents of important enzymes that regulate a wide range of body functions such as respiration, digestion, growth, etc. Once these basic needs are met, then an organism is able to: - Grow and maintain itself for a period of time - Reproduce to perpetuate its species - Mutate to evolve into better adapted life forms. Maintaining life on Earth also requires efficient recycling of dead organisms and the waste produced by living organisms to regenerate the raw materials and keep the life support system on the planet sustainable. Water isn’t just an essential ingredient; it is also an essential medium to bring reacting chemicals together. Liquid water can only exist under restricted conditions of temperature and pressure thus is a relative commodity in the universe and so it determines whether or not a planet can harbour life as we know it. There is a lot of water on Earth and life is very versatile and diverse, as a result there is a large number of species living continuously. Although most of them are very small – roughly 99% of all species are smaller than bees. Also, many species that have existed on Earth have gone Extinct as such is the eventually path of all life on Earth. THE LINNAEAN CLASSIFICATION SYSTEM: Since life on Earth is so diverse, we have a classification system that groups living organisms into categories according to their similarities. These similarities are called Taxonomic Categories. The most widely used mode of classification is based on the work of a Swedish botanist, Karl von Linné. - The highest category in the Linnean Classification System is the kingdom. There are five kingdoms, Monera, Protista, Fungi, Planta (Metaphyta), and Animalia (Metazoa). The organisms in each kingdom are different on the basis of their structural organization and their method of nutrition. o Structural organisation: all living organisms consist of cells; some organisms consist of just on cell (bacteria) whereas others consist of many cells with distinct functions (humans). ▪ There are two types of cells. Prokaryotes and Eukaryotes. • Prokaryote cells evolved first. They have a simpler and more primitive structure. o Membrane (cell wall) that separates the inside and outside of cell. o The material inside the cell wall is the cytoplasm in which all the molecules needed for the cell function are dispersed. • Eukaryote cells evolved later and are more structured. o They have a LARGE nucleus consisting of a membrane enclosing the DNA which contains the genetic instructions for the development and functioning of the cell (the lack of a distinct nucleus is one of the main characteristics of the prokaryote cell). o The cytoplasm also contains cell organelles o Method of nutrition: there are two basis methods modes: autotrophy and heterotrophy ▪ Autotrophs are organisms able to synthesize their food. They produce organic matter from inorganic molecules such as CO 2 nitrate, phosphate, etc. that is obtained from their environment. • They need energy to complete this task: o If they use energy derived from light, they are photoautotroph o If they use energy derived from chemical reactions, they are called Chemoautotrophs. NOTE THAT NO EUKARYOTE CELLS ARE THIS. ▪ Heterotrophs are organisms unable to synthesize their own good and they need to ingest or absorb organic matter produced by other organism. • Heterotrophs oxidize the ingested organic matter during respiration to produce the energy that they need. • Heterotrophs can either be herbivores, carnivores, and decomposers. The kingdom of Monera consists of single cell prokaryotes. This kingdom includes all organism made of primitive prokaryote cells. The method of nutrition within this kingdom is diverse. Some monera are autotrophs while others are heterotrophs. In this kingdom, you’d find all bacteria and blue-green algae. 2 The kingdom of Protisa consists mostly of single celled organisms, but the cells are eukaryotes. There are a few examples of colonial members – all the cells are the same and have similar generalized functions, whereas in truly multicellular species, the body of the organism consists of a variety of types of cells. Humans for example are multicellular – the cells in the brain and the cells in the liver have different functions. Examples of Protisa include Protozoa (heterotrophs) which are animal like single cell organisms such as amoebas and ciliates. Microalgae (photoautotrophs) which are plant like single cell organisms such as diatoms, dinoflagellates. The kingdom of Fungi consists mostly of multicellular organisms. There are all heterotrophs – some examples being mushrooms, molds, yeast, mildew. Organisms belonging to the kingdom of Fungi play an important role in the decomposition of dead organic matter and the recycling of nutrients in terrestrial ecosystems. The kingdom of Plantae/metaphyta consists uniquely of multicellular organisms made up eukaryotic cells that are all photoautotrophs. Another characteristics of the organisms belonging to the kingdom is that they do not have their own means of locomotion – examples include: mosses, ferns, trees, flowering plants, etc. which mostly grow on land and account for about half the organic matter produced by photosynthesis. The kingdom of Animalia/Metazoa includes all multicellular, eukaryotic, heterotroph cells that have their own means of locomotion. This kingdom includes organisms ranging from insects, frogs, lizards, and humans. Photoautotrophs are found in three of the five kingdoms: Plantae (Metaphyta), Protisa, and Monera. Single celled photoautotrophs belong to either the kingdom of Protisa or Monera, whereas multicellular photoautotrophs mostly belong to the kingdom of metaphyta (trees) although seaweed are multicellular protists. The division that occurs after a kingdom is as such, we will do the example for humans. - Kingdom: Animalia – we consist of eukaryotic cells, are multicellular and heterootropic o Phylum: Chordata – all animals with a notochord (supporting rod running most of the length of animals, in our case, the spinal cord) ▪ Class: Mammalia – we have mammary glands, are warm-blooded, bear life young. • Order: Primates – we have colar bones, eyes facing forward, grasping hands with fingers, two types of teeth, incisions and molars. o Family: Hominidae - we have an upright posture, large brain, stereoscopic vision, a flat face, hands and feet with different specialization ▪ Genus: Homo: we have a s-curved spine. • Species: Homo sapiens – high foreheads, well- developed chins, thin skull bones. 3 Recently, we’ve sequenced the genetic code of many organism and thus have a basis for refining the classification of organisms on Earth. Based on similarities and differences of the geneti codes between organisms, the kingdom of Monera has been divided into two separate domains: - The domain of the bacteria - The domain of the archaea Although both groups contain prokaryotic cells, the genetic sequencing seems to suggest that they evolved independently from an ancient common ancestor very early in the evolution of life as they are very different. On the other hand, the genetic codes of all organism made up eukaryotes cells are much closer, hence grouping them into one single domain. - Based on the similarities and differences of the genetic codes between organisms, we can draw a tree with three main branches or domains: Bacteria, Archaea, Eucarya. o The three domains emerge and branch from a common ancestor to all living organisms on Earth. Organisms that have arisen from it are placed at the ends of the tree’s branches – each node on each branch represents the most recent common ancestor of the descendants. The distance of one group from the other groups indicates the degree to relationships. o All these different organisms are not living in isolation but interact with each other: ▪ Some feed on others, producing food chains or food webs. ▪ They compete for resources and living space within the environment o They also interact with and modify their physical surroundings, forming the aforementioned ecosystems. ▪ We distinguish a large number of ecosystems on land and in the ocean (terrestrial/aquatic The surface of the continents can be broadly divided between different ecosystems, which we also sometimes call biomes such as rain forests, coniferous forests, deserts, tundra’s, grasslands, etc. - From space, you can see that on land, there are lush rain forests and dry deserts. The oceans are blue water and the productive regions indicating high concentrations of marine plankton. o This colour depends on the amount of chlorophyll present (chlorophyll is the green pigment that plants use to capture energy from the sun) o Blue = low chlorophyll concentration o The different regions – even in the ocean – are characterized by different ecosystems. - On land, photoautotrophs are mainly multicellular organisms part of the metaphyta kingdom, on the sea photoautotrophs are mostly single cell organism belonging to the kingdom of protisa are called phytoplankton. PLANKTON: Plankton involves small organisms drifting in surface water. Phytoplankton are plant-like whereas zooplankton is animal life. Marine phytoplankton contribute about half the organic carbon produced by photosynthesis on Earth. 4 - Blue-green algae are important contributors to marine plankton in large areas of the ocean - Copepods are tiny shrimp-like organism, are also common members of marine plankton are also common members of marine plankton (they belong to the kingdom of Animalia). In the productive waters in the Southern Ocean, phytoplankton is dominated by relatively large chain- forming diatoms. These relatively large phytoplankton cells support relatively large zooplankton which directly feed fish, mammals and birds resulting in relatively short food chain. In contrast to this, in low productivity regions phytoplankton is dominated by very small flagellates and cyanobacteria which can only be eaten by small micro zooplankton species which then feed larger zooplankton, thus supporting longer and more complex food chain which ends up with large predatory fishes. - The pelagic province is the water column environment, the benthic province is the seafloor environment - Phytoplankton can only grow in the presence of light and light can only penetrate a few tens of meters in the water column. As a result, the ocean is subdivided into two groups based upon the depth of light penetration: o Photic zone which occupies the depth range where light penetration is sufficient for photosynthesis. It extends from the atmosphere-water interface downwards to a depth where light intensity falls to 1% of that at the surface. THIS is where phytoplankton grow. ▪ The depth of this zone varies about 10m on the shelf to about 100m in the open ocean depending on the clarity of the water. o The aphotic zone which is situated below and receives essentially no light because is all absorbed by the water above. o Since the mean water depth is 5000m, most of the water is aphotic and the euphotic zone only included a small fraction of the total volume of the ocean. Organisms living in the sea can also be classified based on lifestyle. 1. Plankton are the organisms which float and drift freely in the water with the currents. They sometimes have limited swimming ability. a. They are divided into phytoplankton and zooplankton 2. Nekton are active swimmers that can move independently of ocean currents. They include fish, reptiles, mammals, birds and others. 3. Benthos are the organisms which live on the surface or within bottom sediments. Organisms living on the surface of sediment are called epibenthic and animals living without sediment are called infauna. Benthic plants need light and thus are restricted to sediment shallow enough to within the photic zone. LEARNING OBJECTIVES: 1. Explain how organisms interact with each other to create food webs and sustainable ecosystems 2. Describe the chemical transformations that occur during photosynthesis, chemosynthesis, nitrogen fixation and respiration 3. Contrast food chains and trophic pyramids in different ecosystems 5 Organisms do not live in isolation but interact with each other and their environment to form ecosystems and any ecosystem can be represented using a diagram. Energy is continuously added and dissipated – the energy for nearly all ecosystems on Earth is provided by the sun and dissipates into the environment as heat produced by the metabolism and movement of organisms. Materials are routinely recycled in food webs/chains. - Plants produce organic matter from inorganic nutrients by photosynthesis - Plants are eaten by herbivores - Herbivores are eaten by carnivores - All of these are decomposed after their death by decompress. As a result of this, carbon and inorganic nutrients are regenerated and released back into the environment. - Regenerated carbon and nutrients are then again taken up by the plants to start the cycle over again Step one in the food chain is done by the autotrophs (organisms able to produce organic matter from inorganic chemical found in the environment). Due to this, they are called “primary producers”. These organisms need energy to produce the organic matter though, if their energy comes from the sunlight, they are called photoautotrophs; if it comes from exothermic chemical reactions they care called chemotropism. - Photosynthesis converts solar energy into chemical energy stored in the chemical bonds of organic matter. 6 molecules of CO are forced to combine with 6 molecules with 6 molecules of 2 water to produce one molecule of organic matter called carbohydrate. 6 molecules of O are 2 also creates as a by-product of this process. o Not just carbohydrates, there are other things such as proteins, molecules containing nitrogen and DNA containing phosphorus. So plants take these molecules in to meet their needs in N and P. - Chemoautotrophs are bacteria or archaea that are found in environment such as deep seat vents, sediments, mid, hot springs, etc. for most ecosystems the external source of energy is sunlight and the primary producers are photoautotrophs. Since plants are found on land and sea – some of the phytoplankton that is found in the sea, dubbed cyanobacteria, is particular important because they are the most numerous organisms on earth and account for half the total primary production in the marine environment. - Many phytoplankton species also produce biominerals – the two most common ones being calcium carbonate and silica (opal). To produce these biominerals, the phytoplankton must also take up dissolved calcium ions (Ca ) to make calcium carbonat
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