IB Biology Notes for Ecology & Conservation A. De Jong/TFSS 2008 1 of 27 The information in this document covers the IB syllabus for topic 5 (not 5.4) and option G. Sections where headings have been highlighted indicate material that is only tested in HL Biology. Introduction to Ecology First, a few definitions: • ecology = the study of relationships between living organisms and between organisms and their environment • ecosystem = a community and its abiotic environment • population = a group of organisms of the same species who live in the same area at the same time • community = a group of populations living and interacting with each other in an area • species = a group of organisms which can interbreed and produce fertile offspring • habitat = the environment in which a species normally lives or the location of a living organism • autotroph = an organism that synthesizes its organic molecules from simple inorganic substances • heterotroph = an organism that obtains organic molecules from other organisms • consumer = an organism that ingests other organic matter that is living or recently killed • detritivore = an organism that ingests non-living organic matter • saprotroph = an organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion • trophic level = the position that an organism occupies in a food chain or a group of organisms in a community that occupy the same position in food chains Types of heterotroph: • herbivores are organisms that consume only plant matter o cows, rabbits, koalas, pandas • carnivores are organisms that consume only animal flesh (and kill their food) o lions, tigers, sharks, orcas • omnivores are organisms that consume both plant & animal matter o humans, bears • piscivores are organisms that consume only fish • insectivores are organisms that consume only insects • sanguivores are organisms that consume only blood of other animals Food chains A food chain is a diagram that shows “what eats what”…basically, how organisms get their food. A food chain is linear, and uses arrows to show the direction of energy flow up the chain. 1. grass cow human mosquito 2. phytoplankton zooplankton herring salmon seal
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IB Biology Notes for Ecology & Conservation
A. De Jong/TFSS 2008 1 of 27
The information in this document covers the IB syllabus for topic 5 (not 5.4) and option G. Sections where headings have been highlighted indicate material that is only tested in HL Biology. Introduction to Ecology First, a few definitions:
• ecology = the study of relationships between living organisms and between organisms and their environment
• ecosystem = a community and its abiotic environment • population = a group of organisms of the same species who live in the same area at the same
time • community = a group of populations living and interacting with each other in an area • species = a group of organisms which can interbreed and produce fertile offspring • habitat = the environment in which a species normally lives or the location of a living organism • autotroph = an organism that synthesizes its organic molecules from simple inorganic
substances • heterotroph = an organism that obtains organic molecules from other organisms • consumer = an organism that ingests other organic matter that is living or recently killed • detritivore = an organism that ingests non-living organic matter • saprotroph = an organism that lives on or in non-living organic matter, secreting digestive
enzymes into it and absorbing the products of digestion • trophic level = the position that an organism occupies in a food chain or a group of organisms
in a community that occupy the same position in food chains Types of heterotroph:
• herbivores are organisms that consume only plant matter o cows, rabbits, koalas, pandas
• carnivores are organisms that consume only animal flesh (and kill their food) o lions, tigers, sharks, orcas
• omnivores are organisms that consume both plant & animal matter o humans, bears
• piscivores are organisms that consume only fish • insectivores are organisms that consume only insects • sanguivores are organisms that consume only blood of other animals
Food chains A food chain is a diagram that shows “what eats what”…basically, how organisms get their food. A food chain is linear, and uses arrows to show the direction of energy flow up the chain.
1. grass cow human mosquito 2. phytoplankton zooplankton herring salmon seal
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Food webs show the interconnections between food chains in a particular ecosystem.
Remember, in food chains & food webs, the arrow indicates, “is eaten by”, so in the web above, algae is “eaten by” both smelt and mosquito larvae. Trophic levels You should be able to identify the trophic level of any organism in a food chain or web.
1. Autotrophs are the first trophic level. They are also referred to as producers. 2. Primary heterotrophs are the second trophic level. Heterotrophs are also called consumers. 3. Secondary heterotrophs are the third trophic level. 4. Etc.
Because of energy losses, most food chains max out with the tertiary or quaternary consumers. Yet another definition… the biosphere is the total of all areas where living things are found; this includes the deep ocean and the lower atmosphere. The biosphere consists of interdependent and interrelated ecosystems. It is organized into biomes, which are large geographical regions with similar climate, flora and fauna. Examples of biomes include tundra, desert, tropical rainforest, boreal coniferous forest, temperate deciduous forest, and grassland.
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Energy in Ecosystems All energy in ecosystems originates from the Sun. Producers (photoautotrophs) convert solar (light) energy to chemical energy (food). Energy flow is unidirectional…it is not recycled. Typically, between 10%-20% of energy is passed on from one trophic level to the next. Energy losses from one level to the next are caused by:
• heat loss through cellular respiration • material not consumed (e.g. bones, beaks, fur, feathers) • material not assimilated – given off as waste
Pyramid of Energy – a diagram that represents the energy at each trophic level. Units are generally kJm-2yr-1.
Pyramid of Biomass – a diagram that represents the amount of biomass (dry weight of organisms) at each trophic level. Biomass gives us a rough estimate of the energy in an ecosystem, since all the molecules in organisms are essentially the same and in the same proportions.
Pyramid of Numbers – a diagram that represents the number of organisms at each trophic level. It may be inverted, if, for example, the ecosystem is a single tree supporting many heterotrophs.
All images from http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/F/FoodChains.html Matter in Ecosystems All matter in ecosystems is recycled. Decomposers and scavengers play a role in this, but are not the only organisms involved. There are specific cycles for carbon/oxygen, water, nitrogen, phosphorus, sulphur, and others.
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Biogeochemical Cycles are the flow of chemical elements and compounds between living organisms and the physical environment. Chemicals absorbed or ingested by organisms are passed through the food chain and returned to the soil, air, and water by such mechanisms as respiration, excretion, and decomposition. As an element moves through this cycle, it often forms compounds with other elements as a result of metabolic processes in living tissues and of natural reactions in the atmosphere, hydrosphere, or lithosphere. (Definition from www.dictionary.com.) The Carbon Cycle
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CarbonCycle.html Carbon exists in the non-living environment in the form of CO2 in the atmosphere (HCO3 when dissolved in water), carbonate rocks such as limestone (CaCO3), fossil fuels and decaying organic matter (e.g. humus in the soil). Carbon enters the living world by the action of autotrophs, which convert carbon dioxide to carbohydrates during photosynthesis (plants & algae) and chemosynthesis (bacteria & archaeans… the only chemoautotrophs). Carbon returns to the non-living world by cellular respiration, burning, and decay.
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Factors Affecting the Distribution of Species Plants
Temperature: most plants live in moderate temperate zones high temperatures denature enzymes & retard growth of plants low temperatures decrease enzyme activity freezing temperatures inactivate enzymes
Water: vital to all living things! needed for enzyme activity, transport, photosynthesis and support adaptations to minimize water loss by transpiration
Light: necessary for photosynthesis and flowering dark areas have few (if any) plants
Soil pH: important for absorption of nutrients acid can cause desertification; limestone can be used to neutralize
Salinity: affects absorption through osmosis high salinity causes water loss (halophiles live in high salt!)
Mineral nutrients: many vital functions Nitrogen for proteins, enzymes, nucleotides, vitamins, etc.
Animals Temperature: high animal distribution in the tropical rainforest
suitable temperature & high availability of producers Water: vital to all living things
low animal distribution in deserts Breeding Sites: for growth and protection of young
high diversity in areas of varied topography Food Supply: animals are heterotrophs
another reason for high animal diversity in the rainforest Territory: for feeding, mating & protecting young
territoriality may be seasonal Niche & The Principle of Competitive Exclusion
Niche = the status of an organism within its environment and community (affecting its survival as a species). No two species can live in the same niche, therefore there is competition for the resources of the land and only one species will survive.
• Fundamental niche is the potential mode of existence of a species, given its adaptations • Realized niche is the actual mode of existence, which results from adaptations and competition
with other species Competitive exclusion is where two species need the same resources and will compete until one species is removed. Inevitably, one species would be more capable, gathering more resources or reproducing more rapidly until the other species was run out of existence. Russian ecologist G.F. Gause demonstrated this concept scientifically using Paramecia:
Species grown separately
Species grown together
Species grown separately
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Community Ecology Interactions between Species:
• competition – for resources such as food, water, shelter, territory, even mates (within a species)
• herbivory – a relationship between a plant and an animal species, where the animal is a herbivore, obtaining energy and organic compounds by consuming part of the plant (rabbits eat grass, giraffes eat leaves off trees)
• predation – a relationship between two animal species, where a carnivore (the predator) hunts and kills another animal; the predator is often larger in size than the prey (lions hunt gazelles, owls hunt mice)
• parasitism – a relationship between a host organism and its parasite; the parasite benefits while the host is harmed (tapeworms are intestinal parasites of many mammals, mistletoe is a parasitic plant that lives on the branches of a tree or shrub)
• mutualism – a relationship between two different species where both organisms benefit (lichens are a mutualistic relationship between a fungus and an alga, pollination benefits both the plant and its pollinator)
Gross Production, Net Production, and Biomass
• Gross production is the amount of material fixed by plants in the process of photosynthesis. • Net production is the amount of material that stays in the body of the plant after spending some
material on respiration. • Biomass is the dry weight of organic matter comprising a group of organisms in a particular
habitat.
Gross Production – Respiration = Net Production If a plant produces 2.0 kg of organic material in a month, and uses 0.95 kg for respiration, the net production is (2.0 – 0.95) kg = 1.05 kg.
Population Ecology The following contribute to the growth of a population:
Growth of a population typically follows a sigmoid (S-shaped) curve:
The sigmoid curve can be divided into three zones:
1. Exponential – no limits on population growth, resulting in a rapid increase in population size. 2. Transitional – intraspecific competition for resources (e.g. food, water, shelter) causes a
decrease in the population growth rate. 3. Plateau – no further increase in the population’s size; the habitat’s carrying capacity has been
reached. Carrying capacity is the maximum number of a species that can be supported by the environment. Factors Limiting Population Growth Density-Dependent Factors affect the population more as the population density (# of individuals per unit area) increases.
• Intraspecific competition • Predation • Disease
Density-Independent Factors affect a part of the population regardless of population density. • weather • natural disasters
Extrinsic Population-Limiting Factors are those factors that come from outside the population. • food supply • predators • disease • weather
Intrinsic Population-Limiting Factors are those factors that come from within the population, including the organism’s anatomy, physiology and behaviour.
• intraspecific competition • self-destructive behaviour (e.g. lemmings) • reproductive behaviours (e.g. only males with blue & purple fur will mate)
0 10 20 30 40 50 60 70 80 90
Num
ber o
f Bac
teria
Time (hh:mm)
Growth of Bacteria
1 2 3
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Types of Populations Open Populations are affected by natality, mortality, immigration & emigration.
• Canada’s human population • A forest
Closed Populations are only affected by natality and mortality.
• Earth’s human population • a test tube • a fish tank
Population Sampling In population studies, it is often useful to know the size of the population in question. Because it is often difficult to count every individual in a population, ecologists use different methods of estimating a population’s size. Random Sample: a method to ensure that every individual in a population has an equal chance of being observed In order for a population study to be effective, the sample must be both random and as large as possible. Population studies are often conducted over a period of days, months or years, depending on the species being studied. Quadrat Study This can be accomplished in different ways.
1. The habitat area can be marked off in a grid, and random sections of the grid are sampled. The sample is used to determine an estimated population size.
Line Transect This may also be done in different ways:
1. Combined with the quadrat study … the quadrat (hoop) is placed at intervals along a line, and only those individuals within the quadrat are counted.
2. All individuals observed along a transect line are counted, and several transects are combined to estimate population size.
Capture-Mark-Release-Recapture (HL only) With mobile organisms such as most animals, it is often difficult to use a quadrat or transect study to estimate population size.
1. Capture a random sample of the organism to be counted. 2. Mark each captured individual with a tag or other marking (shouldn’t interfere with the
organism’s chances of survival). 3. Release tagged individuals back into the habitat. 4. Capture a second random sample, counting how many are marked.
We use the Lincoln Index (below) to estimate the population size:
€
Population Size = n1× n2
n3
n1 = size of 1st sample n2 = size of 2nd sample n3 = # of marked individuals in 2nd sample
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Classification Why do we need to classify organisms? When we classify organisms, we arrange them into groups. Classifying organisms makes them easier to study.
• Classification helps to organize the large number of species into smaller groups, which helps to make sense of the vast diversity of organisms around us.
• Classification attempts to reflect evolutionary links. Species that are in the same group probably share characteristics because they have evolved from a common ancestor, so the classification of groups can be used to predict how they evolved.
• Classification uses common characteristics to group organisms so it helps to predict the characteristics of new members of the group. If several members of a group have a particular characteristic, it is likely that another species in this group will have the same characteristic.
How are Organisms Classified?
All organisms are initially divided into general groupings based on common characteristics such as cell structure and nutrition. The most general division is into domains:
1. Archaea – the archaebacteria, primitive unicellular organisms that live in hostile environments (e.g. high temperature, low pH, high salt) and whose cells do not have a nucleus
2. Bacteria – the eubacteria, unicellular organisms, also without a nucleus, but living in almost any environment (e.g. a mammal’s large intestine, in soil)
3. Eukarya – all organisms whose cells contain a nucleus, which includes animals, plants, fungi and single-celled organisms such as Amoeba and Paramecium
The next grouping of organisms is into kingdoms. Kingdoms Common Characteristics Examples Archae-bacteria
- unicellular - no nucleus (prokaryotic) - few organelles - live in hostile environments
- methanogens, bacteria which produce methane gas as a by-product of cellular metabolism
- extreme halophiles, bacteria that can survive in environments with as much as 15% salt
Eubacteria - unicellular - prokaryotic - few organelles - live in many environments
- Streptococcus group A, which causes strep throat
- Escherichia coli, which lives in the colons of mammals and is found in faeces
Protista - unicellular; some simple multicellular forms
- have a nucleus (eukaryotic) and numerous membrane-bound organelles
- some autotrophs, most are heterotrophs
- Giardia, which causes giardiasis, or “beaver fever”
- Euglena, which have a flagellum and chloroplasts
- Slime moulds, fungi-like protists that can be unicellular or multicellular
- Algae, which may be unicellular or multicellular
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Kingdoms Common Characteristics Examples Fungi - unicellular, multinucleate or
Animalia - multicellular - eukaryotic - heterotrophs - no cell wall
- sponges - corals - insects - birds - mammals
Within a kingdom, organisms are further grouped according to common characteristics. The hierarchy of classification levels, or taxa, is as follows: Species is the most specific, and is the only true classification. It is a group of organisms with similar characteristics, which can interbreed and produce fertile offspring. Genus (pl. genera) is a group of species that are similar. Family is a group of genera that are similar. Order is a group of families that are similar. Class is a group of orders that are similar. Phylum (pl. phyla) is a group of classes that are similar. Kingdom is a group of phyla that are similar. House Cat Redwood Tree Button Mushroom Kingdom Animalia Plantae Fungi Phylum Chordata Coniferophyta Basidiomycota Class Mammalia Pinopsida Hymenomycetes Order Carnivora Pinales Agaricales Family Felidae Taxodiaceae Agaricaceae Genus** Felis Sequoia Agaricus Species** domesticus sempervirens bisporus ** The genus and species name are used as the organism’s scientific name. These names are standard within the scientific community, and are generally based in Latin. Latin names are italicised, with the Genus name capitalized, and the species name not capitalized. Because this gives each organism a two-word name, we call it binomial nomenclature – Carolus Linnaeus, a Swedish botanist & physician originally devised this system in the 1700s.
Dichotomous Keys A dichotomous key is a biological tool for identifying unknown organisms to some taxonomic level (e.g. species, genus, family, etc.). It is constructed of a series of couplets, each consisting of two statements describing characteristics of a particular organism or group of organisms. A choice between the two statements is made that best first the organism in question. The statements typically begin with broad characteristics and become narrower as more choices are required. A dichotomous key is constructed of a series of couplets, each consisting of two separate statements. For example: Couplet 1a. Seeds round…………………………..soybeans 1b. Seeds oblong………………………….2 (The second statement indicates that you need to go to couplet “2”) Couplet 2a. Seeds white……………………………northern beans 2b. Seeds black……………………………black beans By reading the two statements of each couplet, you progress through the key from typically broad characteristics to narrower characteristics until only a single choice remains. As long as the correct statement of each couplet is chosen, and the unknown organism is included in the key, a confident identification is usually achieved. Biodiversity
What is biodiversity? It is the variety of life on our planet. Diversity can be observed between:
• individuals • sub-species (anatomically distinct, but able to interbreed successfully) • species • biological communities • ecosystems
About 10 000 new species are discovered each year. Most of these are insects and other invertebrates; however there are 1-5 new birds and 1-5 new mammals discovered each year, mostly in the tropics. Examples of newly discovered species include:
• Peruvian beaked whale, about the size of a dolphin, discovered in 1976 • Cryptic warbler, a new species of songbird, discovered in Madagascar in 1992
New ecosystems are also being discovered:
• Hydrothermal marine vents on the ocean floor are like submarine hot springs, and are home to hundreds of species, including crabs, shrimps, clams and fishes.
• Anchialine caves, which are flooded caves that are under land, near the coast, and have no direct surface connection with the sea. They are home to many unique crustaceans and other arthropods.
• Lava tubes, which are caves beneath lava flows in Hawaii, and are inhabited by many species of animals that are adapted to life in complete darkness. The primary food source for these animals is the roots of ohia trees that hang down into the caves.
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It is estimated that there are 5 million species of organisms on Earth; 2.1 million of these are insects! The diversity of species in an ecosystem may be quantified using the Simpson diversity index, which takes into account the number of species present and the relative abundance of the species. The inverse or reciprocal of the number calculated represents the probability that two randomly selected individuals from the ecosystem are of the same species.
The formula is:
€
D =N N−1( )n n−1( )∑
N is the total number of individuals in the area n is the number of individuals per species D is the diversity index Example: Two islands each have populations of four species: Island 1 Species n n(n-1) A 345 118 680 B 260 67 340 C 342 116 622 D 598 357 006 Totals 1545 659 648
1/D = 0.276, or 27.6% chance that two randomly selected individuals are the same species. Island 2 Species n n(n-1) A 50 2450 B 20 380 C 40 1560 D 1250 1 561 250 Totals 1360 1 565 640
1/D = 0.847, or 84.7% chance that two randomly selected individuals are the same species. The diversity index values indicate that Island 1 has greater biodiversity than Island 2.
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A high value for D suggests a stable and ancient site. A low D value could suggest pollution, recent colonization or agricultural management (e.g. a monoculture). The index of diversity is usually used in studies of vegetation, but can also be applied to animals or diversity of all species.
o One of the consequences of the pollution caused by the Gulf war was that the diversity of marine species around Bahrain dropped dramatically.
Biomes
• Biome = a major life-zone over an area of the Earth, characterised by the dominant plant life present
• Biosphere = the inhabited part of Earth; includes lower atmosphere, land, and water
Major Biomes of Earth Biome Climate Plant Life
Desert Hot and dry; limited or unpredictable rainfall.
Ephemerals are dormant until there is rainfall, and then go through a quick life cycle to produce seeds. Succulents such as cacti survive year-round due to water-saving adaptations and protective measures such as spines.
Grassland (Temperate)
Moderately dry, with hot summers and cold winters.
Perennial grasses, with some broad-leaf flowering plants that bloom when the grasses are less predominant – at the start/end of growing season.
Savannah (Tropical Grassland)
Three seasons: cool and dry, hot and dry, hot and wet.
Grasses with interspersed, individual trees. Tree population limited by elephants, lightning
Temperate deciduous forest
Four seasons: mean annual temperature 10ºC; 75-150 cm rainfall
Broad-leaf deciduous trees (maple, oak, birch, beech), mosses, ferns, and shrubs.
Boreal coniferous forest
Temperature varies from -50ºC to 30ºC; eight or more months with temperatures below 10ºC. Annual rainfall between 20 & 75 cm.
Coniferous (needle-leaved) trees such as pine and fir; mosses, lichens
Tundra Low temperatures, resulting in permafrost. Arctic Tundra occurs in the far north and Antarctica, while Alpine Tundra occurs well above the tree line on the highest mountains.
Limited growing season in summer and poor soil conditions limit plant life. No trees.
Tropical Rainforest
Areas of heavy rainfall; near the equator. Dominant plants are trees (30-50 m); epiphytes grow on the branches. Most diverse biome on Earth.
The distribution of biomes within the biosphere is affected by both rainfall and temperature.
• Temperature influences organisms’ metabolism; many plants have temperature-dependent phases of their life cycles, such as seed germination after a period of colder temperatures.
• Rainfall is critical, because of the necessity of water for supporting life. Plants that are adapted to a hot, wet climate (e.g. tropical rainforest) would not survive a hot, dry climate (e.g. desert).
Ecological Succession When land is exposed, it doesn’t remain so forever. Organisms quickly move in to the area in a predictable pattern, changing the area over time until it reaches a stable community. This process of change is known as ecological succession. The process of succession is also referred to as a sere, with the stages called seral stages.
• Primary succession occurs when new land is formed, at river deltas, sand dunes, and even lava flows. There is little to no established soil for plants to grow in.
• Secondary succession occurs in areas where the vegetation has been disturbed, by fire or clear-cutting, for example.
Primary succession most often begins with bare rock, the erosion of which forms the mineral portion of soil. Humus, the organic portion of soil, forms from decaying plant and animal matter, and faeces. Until the soil is fully formed, it retains little water (this is also true for sand) even if it is plentiful. A sere that begins in dry conditions such as this is called a xerosere (xerophytes are plants adapted to dry conditions). Primary succession may also occur in aquatic conditions such as a spring-fed pond; this is a hydrosere.
• Pioneer plants are the first plants to live in the new area. Usually, they are small and adapted to life with limited water. Lichens (a symbiosis between a fungus and an alga) are typical pioneer plants.
• Mosses are able to grow once some soil has formed, including humus contributed by the lichens. Other small, herbaceous (i.e. having non-woody stems) plants follow the mosses. Their roots prevent soil erosion, and their deaths enrich the soil by adding more humus.
• The pattern continues with a series of ever-larger plants overtaking the previous community, determined largely by the biome in which the succession is occurring.
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• The final stage is the climax community, a stable ecosystem with characteristic plant and animal life for the biome.
Not every climax community is a forest – introduction of herbivores could change the pattern of succession to result in grassland instead. No matter where succession occurs, each successive stage has greater biodiversity than the one it replaced. Secondary successions occur much more quickly because there is soil present. While primary succession could take several hundred years, secondary succession is often complete within 100 years.
http://www.geogonline.org.uk/images/lithosere.gif
http://www.geogonline.org.uk/images/hydrosere.gif
A hydrosere
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Conservation in the Rainforest Conservation is important on a global scale. While many of these arguments work for any ecosystem, the rainforest in particular is a good example to use, since biodiversity is typically very high in rainforests. Ethical arguments “We did not inherit the earth from our parents; we are merely borrowing it from our children.” (Kenyan Proverb)
• Every species has a right to life, regardless of whether it is useful to humans or not. • The wildlife of each area has cultural importance to the local human population and it is
therefore wrong to destroy it. • It would be wrong to deprive humans in the future of the rich experiences that the Earth’s
biodiversity provides us. Ecological arguments
• Cutting down the rainforest will remove nutrients from the area • The remaining soil is not capable of sustaining many crops. • Erosion will cause further destruction. • Loss of the plant life in the rainforest can increase the amount of CO2 in the atmosphere,
increasing the greenhouse effect and global warming. • Ecologists predict that if we continue without change, nearly half of the world’s species will
disappear in the next 500 years.
Economic arguments • Many of our medicines originate from plants. The rosy periwinkle, once on the verge of
extinction, is now used to produce medicine used in chemotherapy. • The mahogany tree, used for furniture, is a rainforest species. • Recreation and tourism will be affected.
Aesthetic arguments
• Natural ecosystems and species in the wild are beautiful and give us great enjoyment. • Painters, writers and composers have been inspired by the nature around them. • “Extinction is forever.”
Extinction is Forever! (HL only) First, some definitions:
• extinct - species no longer exist anywhere. • extirpated - species no longer exist in the wild in Canada (or another region in which it had
been previously found), but they occur elsewhere. • endangered - species face imminent extinction or extirpation. • threatened - species are likely to become endangered if limiting factors are not reversed. • vulnerable - species are of special concern because of characteristics that make them
particularly sensitive to human activities or natural events.
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Extinct Animals: Although prehistoric animals such as dinosaurs and the sabre-tooth tiger are extinct, they are considered to be natural extinctions. Historic extinctions, on the other hand, are most often caused by the actions of humans.
• The Great Auk – the first North American bird species to become extinct in historic times, it was the only flightless bird in North America, and resembled the penguins now found only in the southern hemisphere. Great auks and their eggs were a source of food to the native people of Newfoundland, but it was the Europeans who caused its extinction, by over-hunting them for food and feathers. The last known nesting pair was killed in 1844 by men who were more interested in the money the birds would bring them.
• The Sea Mink – twice the size of the American Mink, it was hunted to extinction for its fur. The last known member of the species was captured in New Brunswick in 1894.
Extinct Plants: We often think of animals when asked about extinct species, but plant species have become extinct in historic times, also.
• Macoun's Shining Moss is the only Canadian endemic plant to have gone extinct since the 1500’s. It was found only in a small part of Ontario, and clear-cutting of the region where it was found (i.e. habitat destruction) caused its extinction.
• Kerala Legume Tree, was found only in India. It is now extinct due to habitat loss and has not been seen since 1870.
Conservation of Endangered Species: in situ vs. ex situ methods (HL only) Terrestrial and aquatic nature reserves are places where the endangered animal is found in its own natural habitat and is not allowed to be overtaken by humans. This keeps the animals out of danger zones and allows them to live and reproduce naturally in their own environment. Most animals typically tend to survive at a much greater rate using in situ conservation, and preserving their habitat allows other species to live there also, thus preserving other animals and biodiversity. Sometimes in situ conservation methods are not feasible, and other methods (ex situ) are necessary. In captive breeding, animals kept in zoos or parks are allowed to reproduce in order to give them a chance to increase in number, with the possibility of eventually releasing some of the offspring into the wild. Botanic gardens are where most of the known plant species are planted in controlled environments to maintain their species. Seed banks are where seeds are kept, since they stay in good condition for thousands of years. Conservation of Species (HL only)
The International Union for the Conservation of Nature (IUCN) involves 200 governments and 300 private organizations. It focuses on conservation of species and habitats. The IUCN publishes Red Data Books, which are lists of endangered species. The Convention on Trade in Endangered Species (CITES) is an offshoot of the IUCN, and regulates trade in organisms or their products. For example, CITES banned trade in ivory, which was successful in reducing poaching of elephants.
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The IUCN has classified and analyzed areas that have various degrees of biodiversity protection. There are eight categories of protected areas. The first five deal with maintaining biological diversity:
• scientific reserves • national parks • natural monuments • nature reserves • wildlife sanctuaries
The other three categories focus on controlled resource exploitation (e.g. national forests).
One method of conservation is to set up nature reserves. The management of nature reserves involves:
• Control of Alien Species: Alien species must be eliminated, particularly predators and invasive plants.
• Restoration of Degraded Areas: Areas degraded by human activities (e.g. logging, recreation) must be restored.
• Recovery of Threatened Species: Special measures may be needed to help encourage threatened species. For example, supplementary feeding or clearing of vegetation may be required.
• Control of Exploitation by Humans: Exploitation by humans must be controlled. For example, hunting and fishing would be limited or restricted.
In 1992 by the UN Conference on Environment and Development organized the Rio Convention (also called the Earth Summit) in Rio de Janeiro. One of the results of the Rio Convention was the Biodiversity Treaty – countries signing the treaty agreed that richer countries would give money to poorer countries for the conservation of biodiversity.
The World Wildlife Fund (WWF) aims at the conservation of biodiversity by encouraging sustainable use of resources. The WWF is not linked to any government. Greenpeace is another non-governmental organization that is concerned with biodiversity; however, its methods tend to be a bit more controversial than those of the WWF.
r-Strategists and K-Strategists (HL only) Ecologists classify species based on their reproductive strategies. r-Strategists are often pioneer species, colonizing new habitats rapidly. Characteristics of r-strategists include:
• reproduce themselves rapidly • produce large numbers of offspring
• high mortality • short life spans
r-Strategists often occur in numbers well below the carrying capacity for the habitat. Many weeds (e.g. ragweed), insects, and rodents are r-strategists. K-strategists move into settled, stable habitats. Characteristics of K-strategists include:
• reproduce themselves slowly • produce less offspring
• low mortality • long life spans
Once established, K-strategists compete successfully for resources, and population levels remain relatively constant – at the carrying capacity for the habitat.
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Indicator Species and Biotic Indices as a Measure of Environmental Change (HL only) Indicator species are unique environmental indicators as they offer a signal of the biological condition of a watershed or ecosystem. They are also a warning that pollution has entered the food web. The term is actually a bit misleading – indicator species generally refer to whole groups of organisms of a particular type, flora or fauna.
In general, indicator species live all or most of their lives in water, and differ in tolerance to amount and type of pollution. There are four major groups of indicator species:
1. Fish are excellent indicators of the health of a watershed or aquatic ecosystem. a. They are easy to collect with the right equipment.
b. They live for several years.
c. They are easy to identify in the field.
2. Aquatic Invertebrates live in the bottom parts of our waters (benthic organisms). They are
also good indicators of watershed health.
a. They stay in areas suitable for their survival.
b. They are easy to collect.
c. They are easy to identify in a laboratory.
d. They often live for more than one year.
e. They have limited mobility.
f. They are integrators of environmental condition.
3. Periphyton is benthic algae that grow attached to rocks or other plants. They are good biological indicators due to:
a. a naturally high number of species
b. a rapid response time to both exposure and recovery
c. ease of sampling
d. tolerance or sensitivity to specific changes in environmental condition are known for many species
4. Macrophytes are aquatic plants, growing in or near water, submergent (under water), emergent (growing out of water), or floating. Lack of macrophytes in an ecosystem can indicate water quality problems such as herbicide use or salinisation.
A biotic index (BI) is a rating of water quality based on organisms living in a stream. They cannot be determined for lakes or ponds. BI scores are related to dissolved oxygen levels in streams that are affected by inputs to streams. The BI represents stream health over time. Biotic indices are usually regionally developed.
Marine Ecosystems and Fishing (HL only)
The fishing industry vastly increased in scale during the 1970s and 1980s. The number of large ships fishing the world’s oceans doubled and the efficiency of the process was also greatly improved. Nets were catching smaller fish, which were able to escape previous nets in use. Factory ships, sonar fish finders and even helicopters have been used to increase the annual catch.
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Some examples:
• The Grand Banks, off the coast of Newfoundland, has long been a cod fishing-ground. In the early 1990s, the Minister of Fisheries announced that the Grand Banks cod population had reached commercial extinction, and ordered a moratorium on the cod fishery; this put 25 000 people out of work.
• The North Atlantic blue fin tuna is one of the fastest and largest fish in the sea. Until the 1960s it was used only for cat food or sport fishing, but then started being sold in Japan for use in sushi, and its numbers have declined ever since. Tuna fishing is regulated, but due to its commercial value it will likely be hunted to extinction.
• Shark fishing was done mainly for sport until the mid-1970s, when it was marketed as a cheap alternative to swordfish (also greatly over-fished). The industry peaked in the mid-1980s and has plummeted since then.
• Sturgeon fish are hunted for their eggs, which are used in caviar. Four of the eight North American species are listed as endangered or threatened.
Invertebrate fisheries are also an issue. Crab, lobster shrimp and other species are at risk from over-fishing.
• 40% of the world’s shrimp is supplied by aquaculture in countries such as Thailand, Bangladesh, and the Philippines. These countries are being pressured to convert natural mangrove forests and other ecosystems into shrimp farms, seen as an inexpensive way to increase earnings from the industrialized world. However, this would occur at a great environmental cost, as it would destroy habitats for other fish and shorebirds, and could cause erosion and flooding. Half the world’s mangrove forests have disappeared, with more than 50% of these lost to shrimp farms.
• Nearly 70 species of mussels are currently endangered, largely because the United States exports $50 million worth of mussel shells to Japan every year for use in the cultured pearl industry.
Regulation of Fishing
In order to conserve fish populations, the number of fish caught is restricted. In November 1998, the United Nations Food and Agriculture Organization adopted a series of measures to monitor and manage the world’s fishing fleets:
• regularly assessing harvesting capacity of fleets
• maintaining national records of fishing fleets
• developing and implementing national capacity management plans
• reducing and progressively eliminating subsidies that contribute to the build-up of fishing capacity
In addition, the FAO will develop a global register of all fishing fleets operating on the high seas and begin to collect information needed for further analysis of the causes of overcapacity.
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How can you help?
Eat the following sparingly, if at all: Okay to eat:
The greenhouse effect is the rise in temperature caused by the presence of certain gases in the atmosphere. These so-called greenhouse gases include water vapour, carbon dioxide, methane and nitrous oxide, and act the same way the glass walls of a greenhouse do.
A greenhouse is an effective place to grow plants all year long because its glass walls allow in plenty of light, and also trap the heat that is released when light is absorbed by objects inside. This means that even in the coldest winter months, the greenhouse is toasty warm.
Image from http://generalhorticulture.tamu.edu/lectsupl/Temp/P34f1.gif
Without the presence of some greenhouse gases in the atmosphere to trap energy, the Earth’s average temperature would be about 60°F colder. Some greenhouse gases are emitted into the atmosphere by natural sources. For example, swamps and marshes emit methane, while most organisms give off CO2 during cellular respiration. However, increases in the emission of greenhouse gases into the atmosphere over the last several decades have been primarily a result of human activity, and has resulted in global warming. Over the past century, the Earth’s average temperature has increased by 1°F.
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While 1°F does not seem like a large increase, it is still enough to affect global climates – particularly rainfall patterns. Plus, scientists studying the greenhouse effect have predicted that global temperatures will increase by between 2°F and 6°F over the next century. This may also lead to a rise in sea level, and other impacts on plants, wildlife and humans.
How do humans contribute to the greenhouse effect?
• Burning fossil fuels ( )
• Deforestation ( )
• Dairy/beef farming ( ) • Landfills ( )
How might global warming affect us?
• Changing climates will affect habitats and ecosystems worldwide – in the past, these changes have been gradual, allowing organisms time to adapt – this may not be the case in our future.
• Warmer temperatures will contribute to the melting of glaciers – this increase in liquid water will cause a rise in sea level, which will affect coastal habitats and urban areas.
• Warmer temperatures in regions that are currently colder may mean that new crops can be grown – but it may also bring droughts to other places where we currently grow crops.
What can we do to reduce the greenhouse effect & global warming?
• Conserve electricity – power plants are huge emitters of greenhouse gases. • Bike, walk, carpool or take public transit to reduce emissions by personal vehicles. • Plant trees – trees love CO2!! • Recycle, and buy environmentally friendly products that won’t end up in a landfill
somewhere. • Investigate the power of the sun – there are lots of products available that use solar energy –
you can even charge a cell phone using solar energy!
The Ozone Layer & UV Radiation Ozone (O3) is a fairly rare molecule in our atmosphere – about three molecules of ozone for every ten million molecules of air. 90% of this ozone is found in the stratosphere – a layer of Earth’s atmosphere that ranges from about 10 km to 50 km above Earth’s surface. The remaining 10% is found in the lower atmosphere, the troposphere. Stratospheric ozone absorbs biologically harmful UV-B rays, so that only a small amount reaches Earth’s surface. This absorption creates heat, making the stratosphere increase in temperature as altitude increases. In the lower atmosphere, however, ozone is considered to be a pollutant, and has been demonstrated to have harmful effects on crop production, forest growth, and human health. UV radiation makes up about 8% of the total solar radiation that reaches Earth’s surface. Biological molecules may absorb UV radiation, and bonds between atoms may be broken – because of this, UV radiation is harmful to organisms and can do permanent damage. It should not be confused with absorption of solar radiation in the visible spectrum (necessary for photosynthesis) or infrared (heat).
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UV radiation can kill phytoplankton, the sea-going organisms that account for a significant portion of net photosynthesis that occurs in the biosphere. The radiation can also retard growth of terrestrial plants by slowing their rate of photosynthesis, usually a result of irradiative damage and subsequent mutations caused in plant leaves. High levels of UV light can also kill the symbiotic bacteria that fix nitrogen in the root nodules of legumes. UV rays cause skin cancer in humans in prolonged exposure or in very high dosages, and can also weaken and potentially destroy the cells of the immune system. Depletion of the Ozone Layer Chlorine reacts with ozone, converting it to oxygen, in an irreversible reaction. One chlorine atom can react with 100 000 ozone atoms. The main source of chlorine atoms in the atmosphere is CFCs, chlorofluorocarbons, used for over 50 years as a refrigerant and as propellants in aerosol cans.
€
O3 + Cl→ClO+O2ClO+O→Cl +O2
Since atomic oxygen is present in the atmosphere from the ozone-production cycle, the chlorine atoms are regenerated by the second reaction and can go on to degrade more ozone. To reduce the release of ozone- depleting substances into the atmosphere, filters can be fitted on factory chimneys to absorb and react with gases
Image from http://www.ozonedepletion.info/education/part3/Image5.gif
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before they escape into the atmosphere, removal of sulphur from gases before they are emitted into the atmosphere, using alternative sources of energy such as wind, hydroelectric, solar, tidal, geothermal and others, use of methane and alcohol as fuels since they do not release sulphur and other harmful gases into the atmosphere. Two of the largest sources of ozone-depleting substances come from the production of recycling refrigerants and the use of chlorofluorocarbons (CFCs) for propellants in spray cans, hairspray, etc. In order to reduce these sources, a ban on CFC-based propellants has been enacted, and most corporations now recycle the refrigerants used rather than produce entirely new ones. Bioaccumulation & Biomagnification Bioaccumulation refers to an increase in the concentration of a chemical in the tissue of an organism over time. Whereas, biomagnification refers to the increased concentration of a toxic chemical the higher an animal is on the food chain. Chemical toxins build up into higher concentrations as they are passed up the food chain. Toxins that commonly bioaccumulate include mercury, DDT and other pesticides, and poly-chlorinated biphenyls (PCBs).
Image from http://web.bryant.edu/~dlm1/sc372/readings/toxicology/biomagnification.jpg
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The Effect of Sewage & Fertilizers on Rivers Water polluted by raw sewage and nitrate fertilizers will become rich in nutrients in a process called eutrophication. The algae absorb large amounts of nitrates, resulting in quick growth and reproduction of these algae. The ecosystem becomes overpopulated with algae (this is called algal bloom). This blocks the sun from reaching the plants at greater depths and blocks the entry of carbon dioxide and oxygen from the atmosphere. The algae hit their carrying capacity and start to die quickly, encouraging the growth of bacteria of decomposition, which increase the biochemical oxygen demand. They consume a large amount of oxygen, which results in deoxygenation of the water and aerobic organisms start to die. Finally, disease-causing anaerobic bacteria and some parasites come in. This makes it a bad spot for anything to survive in. Raw sewages can also release pathogens into the bathing and drinking water supplies, causing the risk of human and animal infection when this water is used. Acid Precipitation Acid precipitation occurs primarily because of the presence of sulphur oxides and nitrogen oxides in the atmosphere. These compounds, which come from smokestacks, industries, and vehicle exhaust, react with water in the air to form acids. These acids can return to the surface as acid precipitation (rain, snow, etc.). On the ground, acid precipitation can affect the solubility of minerals in the soil. It can lower the pH of lakes and contaminate freshwater habitats. It affects fish, amphibians and aquatic invertebrates the most, due to the destruction of their freshwater lake and river environment. Use of Biomass for Fuels Biomass can be used as a source of fuels such as methane and ethanol. Organic rubbish such as remains of food, are placed in a sealed container. Methanogenic bacteria such as Methanobacillus and Methanococcus are added. The container must be sealed to ensure anaerobic reactions. Bacteria decompose organic material in the rubbish to methanoate, ethanoate or methanol. Bacteria use these things as a source of hydrogen (electrons). The hydrogen is used to reduce carbon dioxide into methane. The methane is then released. This can be a source of fuel in factories and industries.
