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BIOL 1070:
MIDTEBIODIVERSITY – EVOLUTION
AND ECOLOGY QUIZ.Verified Global Biodiversity: ▪ Global biodiversity is the total outcome of the two opposing processes:
- Speciation – increase in diversity
- Extinction – decrease in diversity ▪ These two processes and needed to understand the diversity of life Forest Biodiversity Characterizing Diversity: ▪ Within a habitat: o Alpha (α) species diversity - # of species within a habitat ▪ We know the measurement is accurate if we know the number of species per specified collection/sample OR if we know the specified number or individuals o Species evenness – relative abundance of species in an area ▪ High evenness vs. low evenness ▪ Described using the Shannon Diversity Index (SDI): H’ = - ∑ ni x ln(ni)
o SDI is a way of calculation how abundant each species is relative to the abundance of the other species in a habitat – measures EVENNESS o Common sense version of equation: ▪ Across habitats: o Beta (β) species diversity – a measure of how different diversity is between different habitats ▪ Example: o
o It is found at high elevations and in cold environments o Trees cannot tolerate the environmental conditions beyond the tree line (usually cold temperatures or a lack of moisture) o Factors that limit the tree line: ▪ Shade (cool) – competition for water ▪ Full sun (hot) – no competition for water ▪ Full sun (hot) competition for water ▪ Treatments: o Underneath herbaceous canopy (shaded, competition for water) o On bare soil (a lot of light, no competition) o On bare soil, surrounded by herbaceous canopy (a lot of light, competition for water) Overlapping of Competitors:
- Competitive exclusion – one of the species disappears from that area
- Character displacement – both species continue to co-exist, but they diverge to occupy slightly different ecological niches within the shared habitat ▪ Example:
Niche differentiation (realized niche) – natural selection for larger and smaller beak sizes due to competition for food
- Co-existence at reduced carrying capacity – both species continue to live in the area, but at lower numbers of individuals per species ▪ Biodiversity: ▪ Refers to the different scales of biological variation ▪ Comprised of three scales of variation: genetic, species and ecosystem ▪ The Rio Summit definition – the variation of living organisms and the diversity within the species between the species of the ecosystem ▪ The Canadian Biodiversity Strategy – the variation of species and ecosystems on Earth and their ecological processes Species Richness: ▪ The number of species present in an area such as a community or ecosystem ▪ The appropriate sampling intensity required to estimate richness is determined by plotting the number or new species observed with each sampling unit (as shown below):
▪ Examples of species interactions: o Mutualism can be obligate (must live with its partner species) or facultative (can live without its partner species) ▪ Example of ants, plants and aphids: o Aphids feed on the sap within phloem cells of plants which negatively affects the plant (predation) o Ants and aphids benefit from each other because the ants benefit from the excess sap due to the aphids and the aphids are benefited by the ants because in return, the ants protect the aphids from predators (mutualism) Abundance: ▪ Species abundance – how common a species is in a defined area o Can be measured as percent cover (measure of influence), biomass (fuel developed from organic matter) or frequency of individuals per species ▪ Relative abundance – refers to the comparison of the species abundance within a defined area and relates to the “evenness” of the distribution of individuals in a species within a community. Although different communities may have the same species, they can differ in the relative abundance
o Example: each community may contain 10 species and 210 individuals, but in one community all species are equally common (21 individuals of each species = high evenness) and in another community some species are common and others are rare (low evenness) Abiotic: ▪ The physical and chemical features of an environment (non-living) that affect the ability of organisms to survive and reproduce ▪ Abiotic features include: o light (radiation) o temperature (heat) o water (availability, composition and flow) o chemical products o atmosphere o soil conditions (nutrients and porosity)
Intermediate Disturbance Hypothesis (IDH): ▪ Predicts that the highest species richness will occur at an intermediate level of intensity/frequency of natural disturbance: o Low levels don’t create many habitats to support a variety of species ▪ An non-severe fire may transform a maple woodlot into a woodlot that is dominated by ash ▪ When a tree falls in a woodlot it creates a “gap” that has higher levels of light – this gap supports a new community of species that are suited to high light conditions and establish themselves by out-competing other shade tolerant species o High levels eliminate many habitats that support species diversity ▪ Large disturbances – floods, forest fires and hurricanes
▪ A severe fire could transform a woodlot into an open field dominated by herbs and grasses Niche: ▪ Niche is the set of abiotic and biotic conditions in which a species is able to persist and maintain stable population sizes ▪ The ecological niche theory: o Environmental space – the space that an organism occupies in regards to the environmental variables to which the species responds ▪ The ecological niche is sub-divided into the fundamental and the realized niche: o Fundamental niche – the environmental conditions that a species can survive and persist with; however, the species may not be present within all of this space ▪ Ex: geology, landscape, soil o Realized niche – the environmental and ecological conditions that a species can actually survive and persist with ▪ Ex: dispersal ability ▪ The image below on the left shows the fundamental and realized niche’s of moisture and temperature of a woodlot and the example below on the right is a specific example
Urbanization: ▪ Urbanization can increase species richness – especially at intermediate levels of development (related to the intermediate disturbance hypothesis) ▪ Not all plants and animals respond in the same way to disturbances: o A study found that butterfly diversity was highest in areas of intermediate disturbance but another study found that intermediate disturbances facilitated the establishment of non-native ant species that would normally be displaced by native ant species ▪ Biotic Homogenisation: o The domination or urban natural areas by non-native species. o An invasion may increase the total species richness but decrease the diversity of native species o Urbanization = increase in non-native species and decrease in native species Population: ▪ The collection of individuals in a species within an area at a specific time ▪ Population ecology factors include: population size, population density, patterns of dispersion, age distributions and population growth ▪ Population studies may involve questions related to how species abundance changes over time and the factors that affect population growth (ex; food, habitat, disease, predation) ▪ Population Growth: o The change in the # of individuals throughout a period of time o Calculated using demographic data: ▪ population growth rate = birth rate – death rate +immigration –
emigration ▪ ▪ Population Control: o Density-Dependence – factors that affect birth and death rates (population growth/decline) in a way that depends on population density (ex; the effect is stronger/weaker depending on whether the population is dense/sparse)
o Elements are continuously recycled from ecosystems – the flow of energy and the cycling of materials o Flow of energy – must be continuous because heat energy cannot be recycled ▪ The light energy is captured by plants through photosynthesis which results in the production of organic molecules which are later converted to heat through respiration o Cycling of materials: ▪ Elements occur within ecosystems through processes such as breaking down of parent molecules (ex; rock) ▪ Plants take up elements from the soil, water or air which animals consume from the plants or they may directly consume them from the environment through water or consuming mineral soil. Animals release minerals through excretion and bacteria and fungi facility the decomposition of these minerals ▪ Ecosystem Function: o Includes the exchange or energy and nutrients among plants, animals and their environment
▪ Ex: in a woodlot there is carbon in the form of branches, logs and leaf litter that is decomposing and producing biomass that organisms (such as insects, bacteria and fungi) feed off of, keeping them from piling up on the woodlot floor ▪ Ex: there is a fungus decaying log on the floor of the Goose Walk woods in the arboretum ▪ Ex: there is a stand of choke cherry that has an infection or pathogenic fungus in the Dairy Bush Habitat: ▪ A habitat is the environment where a species is known to occur ▪ Can be considered environmental space (the space that an organism occupies which is influenced by abiotic and/or biotic environmental variables ▪ Can include any characteristic of the environment (food quality) and the use of a specific geographic area by an animal or plant (mountain meadow) ▪ Habitats can be either large or small o Large – the woodland caribou’s habitat is boreal (northern region) forest biome o Small – a species of lichen may only occur on acidic rocks ▪ You must understand habitat diversity within an ecosystem to sample biodiversity since if you miss key types of habitats then you may not have sampled all of the biodiversity within the ecosystem ▪ Higher habitat diversity usually means there is higher species richness in ecosystems
species of plants cannot survive or establish tree seedlings (this is the competitive exclusion principle) Carrying Capacity: ▪ # of individuals that can survive on the available resources in an area ▪ Carry Capacity is not fixed because it can be altered by disturbances ▪ Decrease in resources = decrease in carrying capacity, therefore decrease in population size ▪ The graph to the right shows a population growing over time – the population size reaches a maxium that can be sustained by the resources; this is shown by the line labeled “carrying capacity” Ecosystem Engineering: ▪ Ecosystem engineers are organisms that can control the availability of resources to other species – they can change, sustain and develop new habitats and influence the niche of other species ▪ Niche construction is a feedback mechanism (a response in a system that influences the activity/productivity of the system – can be positive or negative feedback) of natural selection communication forces on the abiotic niche
▪ Organisms can modify conditions locally (ex; a woodlot) and globally (ex; boreal forest region) over time and even after death (ex; decaying logs) ▪ Example - the influence of Alder shrubs on the progression in the boreal forest ecosystem: o Alder species have a symbiotic relationship (mutual beneficial) with Frankia alni. o Frankia alni is a nitrogen-fixing bacterium; take nitrogen from the atmosphere and convert it to a form that is used by plants such as an Alter tree and in return, Alder provides Frankia alni with carbon that the tree produces during photosynthesis – BOTH BENEFIT (symbiotic) o Alder is one of the first woody plants to establish itself after a disturbance (pioneer species). It improves the fertility of the soils where it grows and helps provide additional nitrogen for the following establishing species (such as balsam fir and spruce) Adaptive Management:
