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By Chris Paine
https://bioknowledgy.weebly.com/
C.1 Species and Communities
Essential idea: Community structure is an emergent property of an ecosystem.
The image shows savannah grassland. The community of animals (here grazing Antelope, Zebra and Wildebeest) are present only due to the grassland environment, which in itself is a function of the grazing animals. Grazing is a key element along with fire and soil fertility that maintains the savannah. Without these elements in balance the savannah would either be succeeded by bush and forest or deteriorate into desert. A good example of how a community can be an emergent property of an ecosystem, whilst still being a critical part of the ecosystem.
http://rydberg.biology.colostate.edu/knapplab/Research/SA2007%20diverse%20grazers%20comp.jpg
Understandings
Statement Guidance
C.1.U1The distribution of species is affected by limiting
factors.
C.1.U2 Community structure can be strongly affected by
keystone species.
C.1.U3
Each species plays a unique role within a
community because of the unique combination of
its spatial habitat and interactions with other
species.
C.1.U4 Interactions between species in a community can
be classified according to their effect.
C.1.U5 Two species cannot survive indefinitely in the
same habitat if their niches are identical.
Applications and Skills
Statement Guidance
C.1.A1
Distribution of one animal and one plant species
to illustrate limits of tolerance and zones of
stress.
C.1.A2 Local examples to illustrate the range of ways in
which species can interact within a community.
C.1.A3
The symbiotic relationship between
Zooxanthellae and reef-building coral reef
species.
C.1.S1
Analysis of a data set that illustrates the
distinction between fundamental and realized
niche.
C.1.S2 Use of a transect to correlate the distribution of
plant or animal species with an abiotic variable.
C.1.U1 The distribution of species is affected by limiting factors.
C.1.U1 The distribution of species is affected by limiting factors.
Factors affecting the distribution of species:
Plants Animals
temperature
water
light (intensity/wavelength) breeding sites
soil pH food supply
soil salinity territory
mineral nutrient availability
n.b. apart from being able to list the different factors you should know examples of how certain factors have influenced the distribution of example species.
C.1.U1 The distribution of species is affected by limiting factors.
Example factors affecting the distribution of species
Woody species of plants (e.g. Oak and Maple trees) synthesise ‘antifreeze proteins’ which prevents the formation of ice crystals inside cells. This enables these species to survive in temperatures as low as -40 oC. These species cannot survive at high temperatures as they transpire readily and will therefore dehydrate easily.
Low temperature adaptation in plants
http://upload.wikimedia.org/wikipedia/commons/thumb/f/f7/BrockenSnowedTrees.jpg/1024px-BrockenSnowedTrees.jpg
C.1.U1 The distribution of species is affected by limiting factors.
Example factors affecting the distribution of species
“Southern right whales migrate from their Antarctic feeding areas to temperate breeding areas along the costs of Chile and Argentina, southern Africa, and Australia and New Zealand, covering 2,500 km each way. Their migration is fuelled entirely by fat accumulated during their four-month stay in the icy Southern Ocean around Antarctica, where they skim the surface waters for zooplankton. Amazingly, they will not feed until their return a year later.” http://www.nature.com/scitable/knowledge/library/animal-migration-13259533
Migration for food supply in animals
http://upload.wikimedia.org/wikipedia/commons/c/c2/Southern_right_whale6.jpg
C.1.U1 The distribution of species is affected by limiting factors.
Example factors affecting the distribution of species
Territory availability and distribution of animals
• Tigers are solitary animals that require large territories, the size of which is determined mostly by the availability of prey.
• A tiger’s territory consists of forest, to shelter their prey, and access to water.
• Although individuals do not patrol their territories, they visit over a period of days or weeks and mark their territory with urine and feces.
Their habitat has been lost to growing human populations which require land for agriculture. Both the size of forest patches has decreased, some are too small to support individual tigers and total size of habitat has decreased lowering the maximum population size.
http://upload.wikimedia.org/wikipedia/commons/1/16/Indian_Tiger.jpg
C.1.U1 The distribution of species is affected by limiting factors.
Temperature - plant can only survive in a range of temperatures to which they are adapted• Metabolic pathways are controlled by enzymes, which have optimal temperatures, too
high and the enzymes will denature• High temperatures increase the rate of evapouration (and hence transpiration)
Water availability limits plant growth in most terrestrial ecosystems• Needed to maintain cell turgor• Needed for photosynthesis and respiration to occur• Xerophytes, e.g. Cacti are adapted to low water conditions, hydrophytes, e.g. rice, are
adapted to waterlogged soils
Light (intensity/wavelength) limits the plants ability to carryout photosynthesis.• Plants that grow in shade (lower light intensity) contain more chlorophyll, they have
darker green leaves• Plants, e.g. Kelp (algae), appear brown, not green, and have pigments that are adapted to
absorbing the blue wavelengths as red wavelengths do not easily penetrate water
Detail on how the factors affecting the distribution of Plant species:
n.b. Although it is unlikely you will need to learn all of these details understanding the concepts will enable you to better communicate your examples.
C.1.U1 The distribution of species is affected by limiting factors.
Most plants only tolerate a narrow Soil pH range• pH affects the availability of mineral nutrients, e.g. minerals can either be bound more
strongly in the soil or leeched from the soil more easily at different pHs.• pH may affect the decomposition of organic matter, and hence the rate at which
nutrients are (re-)cycled and made available to plants
Most plants have a low Soil salinity tolerance or can only tolerate a narrow range of salinity• High salinity either makes uptake of water (osmosis) by plants more difficult, or in
extremes causes water loss• Halophytes, e.g. Mangrove trees, are adapted to high salinity soils
Minerals nutrient availability affects plant fertility, different plants need minerals (e.g. Nitrogen, Phosphorus and Potassium) in different quantities.• Waterlogged soils encourage denitrifying bacteria and lower the nitrogen availability to
plants• Weathering of rocks often increases the availability of nutrients in the soil
Detail on how the factors affecting the distribution of Plant species:
n.b. Although it is unlikely you will need to learn all of these details understanding the concepts will enable you to better communicate your examples.
C.1.U1 The distribution of species is affected by limiting factors.
Temperature must be within a viable range (based on adaptations) for survival – few animals can survive extreme temperature conditions• Body size (specifically SA:Vol ratio) will determine an animal's ability to conserve heat – a
large SA:Vol ratio means that heat is easily lost to /gained from the environment• Homeotherms (organisms that maintain a stable internal body temperature) can colonise
a wider range of habitats than poikilotherms (internal temperature varies considerably)
Water must be available in quantities sufficient for the particular species concerned.• Apart from drinking to maintain cells’ osmotic balance water can be required as a habitat,
transport medium, a place to lay eggs, a source of dissolved oxygen, food maybe filtered from water (e.g. corals), and as a coolant. [See 2.2 Water for details]
Breeding sites are required for the maintenance of the species.• Breeding sites need to provide protection for eggs, juveniles, and nesting adults.• Sites are often rich in food or other resources necessary for juveniles, and breeding adults• Juveniles may have specialised environmental requirements different from the adults,
e.g. dragonfly nymphs live underwater.
Detail on how the factors affecting the distribution of animal species:
n.b. Although it is unlikely you will need to learn all of these details understanding the concepts will enable you to better communicate your examples.
C.1.U1 The distribution of species is affected by limiting factors.
Food availability is critical in determining the maximum population size.• Animals maybe specialised so that they will only consume a particular species of animal
or plant, e.g. the caterpillars of the Small Tortoiseshell butterfly eat only nettle plants.• Seasonal or geographical variation in food directly affects abundance of the population.
Territory – not all animals are territorial, but those that may do so to attracting mates, rearing young, forage for food or to avoid predators.• Animals may mark territories, e.g. by urinating or marking trees• Territories can be established by individuals, breeding pairs or groups• Territories maybe temporary (e.g. just for the duration of breeding cycle) or permanent• Establishment of territories can lead to intra-specific (within species) or inter-specific
(between species) competition
Detail on how the factors affecting the distribution of animal species:
n.b. Although it is unlikely you will need to learn all of these details understanding the concepts will enable you to better communicate your examples.
C.1.S1 Use of a transect to correlate the distribution of plant or animal species with an abiotic
variable.
C.1.S1 Use of a transect to correlate the distribution of plant or animal species with an abiotic
variable.
C.1.S1 Use of a transect to correlate the distribution of plant or animal species with an abiotic
variable.
C.1.S1 Use of a transect to correlate the distribution of plant or animal species with an abiotic
variable.
C.1.S1 Use of a transect to correlate the distribution of plant or animal species with an abiotic
variable.
C.1.A1 Distribution of one animal and one plant species to illustrate limits of tolerance and zones of
stress.
Shelford's law of tolerance is a useful tool to understand the relative abundance of a species and hence predict community structure. It plots the range of a biotic or abiotic factor that is tolerated by a species,. Because their is variability but within a population the limits of tolerance and where the zones of stress start is not always easy to measure.
http://www.anselm.edu/homepage/bpenney/teaching/BI320/elements/Krohne_Shelfords.jpg
C.1.A1 Distribution of one animal and one plant species to illustrate limits of tolerance and zones of
stress.
Black mangrove (Avicennia germinans) is a very widespread mangrove tree. It can survive and grow in a wide range of salinity levels from 0 to 96 part per thousand (ppt). Greatest growth rates occur at salinity levels of 24 and 48 ppt, the optimal zone, outside of this range the Black Mangrove trees experience the zones of stress.
http://commons.wikimedia.org/wiki/File:Avicennia_germinans.jpg
C.1.A1 Distribution of one animal and one plant species to illustrate limits of tolerance and zones of
stress.
http://commons.wikimedia.org/wiki/File:Coral_reef_locations.jpg
http://commons.wikimedia.org/wiki/File:20_Grad_Isotherme.png
The red dots show the global distribution of coral reefs.
Here is a clue - the blue band shows where water temperatures are in excess of 20oC.
Q - What causes this distribution?
C.1.A3 The symbiotic relationship between Zooxanthellae and reef-building coral reef species.
Most reef-building corals contain photosynthetic algae, called zooxanthellae, that live in their tissues (endosymbiosis).
The corals and algae have a mutualistic relationship*
http://oceanservice.noaa.gov/education/kits/corals/coral02_zooxanthellae.html
https://microbewiki.kenyon.edu/index.php/File:Zoox_1.jpg
http://commons.wikimedia.org/wiki/File:Multy_color_corals.JPG
*Mutualistic relationship is an association between organisms of two different species in which each member benefits.
C.1.A3 The symbiotic relationship between Zooxanthellae and reef-building coral reef species.
The coral provides the algae with:• a protected environment - coral polyps
secrete calcium carbonate to build the stony skeletons which house the coral polyps (and zooxanthellae)
• compounds they need for photosynthesis
The corals and algae have a mutualistic relationship
The algae provide the coral with:• Oxygen• helps the coral to remove wastes• Supplies the coral with glucose, glycerol,
and amino acids (products of photosynthesis)
The relationship between the algae and coral polyp facilitates a tight recycling of nutrients in nutrient-poor tropical waters.
zooxanthellae are responsible for the unique and beautiful colors of many corals
http://oceanservice.noaa.gov/education/kits/corals/coral02_zooxanthellae.html
http://commons.wikimedia.org/wiki/File:Multy_color_corals.JPG
C.1.A1 Distribution of one animal and one plant species to illustrate limits of tolerance and zones of
stress.
Photosynthesis pathways in zooxanthallae are impaired at temperatures above 30oC therefore for most corals the upper limit of tolerance is 30oC
The maps show that for most coral species that the limits of tolerance for most species is approximately 20oC.
Corals live in very nutrient poor waters and have certain zones of tolerance to water temperature, salinity, UV radiation, opacity, and nutrient quantities.
Coral reef bleaching, the whitening of diverse invertebrate taxa, results from the loss of symbiotic zooxantheallae and/or a reduction in photosynthetic pigment concentrations in zooxanthellae
Favia pallida (hard coral) with signs of
bleaching
http://commons.wikimedia.org/wiki/File:Favia_pallida_(hard_coral)_with_signs_of_bleaching_or_crown-of-thorns_starfish_damage.jpg
C.1.U4 Interactions between species in a community can be classified according to their effect.
C.1.A2 Local examples to illustrate the range of ways in which species can interact within a
community.
C.1.U4 Interactions between species in a community can be classified according to their effect.
C.1.A2 Local examples to illustrate the range of ways in which species can interact within a
community.
C.1.U4 Interactions between species in a community can be classified according to their effect.
C.1.A2 Local examples to illustrate the range of ways in which species can interact within a
community.
C.1.U4 Interactions between species in a community can be classified according to their effect.
C.1.A2 Local examples to illustrate the range of ways in which species can interact within a
community.
C.1.U4 Interactions between species in a community can be classified according to their effect.
C.1.A2 Local examples to illustrate the range of ways in which species can interact within a
community.
C.1.U4 Interactions between species in a community can be classified according to their effect.
C.1.A2 Local examples to illustrate the range of ways in which species can interact within a
community.
C.1.U3 Each species plays a unique role within a community because of the unique combination of
its spatial habitat and interactions with other species.
C.1.U3 Each species plays a unique role within a community because of the unique combination of
its spatial habitat and interactions with other species.
C.1.U5 Two species cannot survive indefinitely in the same habitat if their niches are identical.
C.1.S1 Analysis of a data set that illustrates the distinction between fundamental and realized
niche.
C.1.U5 Two species cannot survive indefinitely in the same habitat if their niches are identical.
C.1.S1 Analysis of a data set that illustrates the distinction between fundamental and realized
niche.
C.1.U5 Two species cannot survive indefinitely in the same habitat if their niches are identical.
C.1.U5 Two species cannot survive indefinitely in the same habitat if their niches are identical.
C.1.U2 Community structure can be strongly affected by keystone species.
http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/15829742/f1_wagner.jpg
keystone species exerts top-down influence on lower trophic levels and prevents species at lower trophic levels from monopolizing critical resources, such as competition for space or key producer food sources.
A keystone species is one which has a disproportionate effect on the structure of an ecological community.
C.1.U2 Community structure can be strongly affected by keystone species.
http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/15829742/f1_wagner.jpg
The term keystone species was first coined by Robert Paine (1966):• One of his study sites, located
at Mukkaw Bay, contained a community consistently dominated by the same species of mussels, barnacles, and the starfish, Pisasterochraceus, which preys upon the other species as a top predator.
• He selected a "typical" piece of shoreline at Mukkaw Bay, about 8 meters long by 2 meters wide, that was kept free of starfish.
• This area was compared to an adjacent, undisturbed control area of equal size.
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
C.1.U2 Community structure can be strongly affected by keystone species.
http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/15829742/f1_wagner.jpg
The intertidal area where Pisaster had been removed was characterized by many changes:• Remaining members of the ecosystem's food web immediately began to compete with
each other to occupy limited space and resources.• Within three months of the Pisaster removal, the barnacle, Balanus glandula, occupied
60 to 80% of the available space within the study area.• Nine months later, Blanus glandula had been replaced by rapidly growing populations
of another barnacle Mitella and the mussel Mytilus.• This phenomenon continued until fewer and fewer species occupied the area and it
was dominated by Mytilus and a few adult Mitella species.• Eventually the succession of species wiped out populations of benthic algae.• This caused some species, such as the limpet, to emigrate from the ecosystem because
of lack of food and/or space.• Within a year of the starfish's removal, species diversity significantly decreased in the
study area from fifteen to eight species.
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
C.1.U2 Community structure can be strongly affected by keystone species.
http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/15829742/f1_wagner.jpg
Within a year of the starfish's removal, species diversity significantly decreased in the study area from fifteen to eight species.
http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/15829770/f2_wagner.jpg
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
C.1.U2 Community structure can be strongly affected by keystone species.
http://www.vanaqua.org/files/1013/2018/0738/otter-eat.jpg
Sea otters regulate sea urchin populations, which in
turn feed upon kelp and other macroalgae (Duggins 1980). The otters keep the sea urchin populations in check, thus allowing enough kelp forests to remain as a habitat for a variety of other species. As a result, the entire ecosystem is kept in balance.
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
C.1.U2 Community structure can be strongly affected by keystone species.
http://commons.wikimedia.org/wiki/File:Beaver-Szmurlo.jpg
Keystone modifier species, such as the North American beaver (Casor candensis), determine the prevalence and activities of many other species by dramatically altering the environment.
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
C.1.U2 Community structure can be strongly affected by keystone species.
Species like the Saguaro cactus (Carnegiea gigantea) in desert environments and palm and fig trees in tropical forests are called keystone host species because they provide habitat for a variety of other species. Keystone prey are species that can maintain their numbers despite being preyed upon, therefore controlling the density of a predator.
http://www.nature.com/scitable/knowledge/library/keystone-species-15786127
http://commons.wikimedia.org/wiki/File:Carnegiea_gigantea_Saguaro_NP_1.jpg
