Lecture 15 and 16 Population Interactions and Community Ecology PDF

Chapter 53 Population Interactions and Community Ecology Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. ...

Chapter 53 Population Interactions and Community Ecology Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Recap What does a population's age structure describe? What is age-specific survivorship? A) The total number of individuals in the population. A) The proportion of individuals alive at the start of an age interval that died during that age interval. B) The average age of individuals in the population. B) The proportion of individuals alive at the start of an age interval C) The relative numbers of individuals in each age class. that survived until the start of the next age interval. D) The geographic distribution of the population. C) The proportion of individuals born in a population during a specific year. Why is the sex ratio important in understanding D) The proportion of individuals that emigrate from a population population growth? during a specific year. A) It determines the total population size. What primarily contributes to increases in population? B) It influences the average age of individuals. A) Immigration and emigration. C) It reflects the recent growth history of the population. B) Birth and Immigration. D) It can impact population growth potential, with a focus on C) Birth, death, immigration, and emigration. females. D) Environmental factors. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. What is a cohort? What is the main characteristic of a Type III survivorship curve? A) A group of individuals from different populations. A) High survivorship throughout life. B) A group of individuals from different species. B) Constant mortality rate across all age classes. C) A group of individuals born at the same time and belonging C) High juvenile mortality followed by low mortality once offspring to the same species and population. reach a critical size. D) A group of individuals with varying ages. D) High mortality in old age. What does the per capita birth rate (b) in a population represent? In the logistics model of population growth, what does A) The number of deaths in the population during a specified period. intraspecific competition refer to? B) The change in population size over time. A) Competition between individuals of different species. C) The number of births per individual in the population. B) Competition for limiting resources between individuals of the same species. D) The average time it takes for an individual to reproduce. C) Competition between different populations. If the per capita growth rate (r) in a population is greater than zero (r > 0), what does this indicate about the population's D) Competition between predators and prey. growth? A) The population is stable. B) The population is decreasing. C) The population is growing. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be D) to scanned, copied or duplicated, or posted The population a publicly is aging. accessible website, in whole or in part.  Learning Objectives 1. Explain how population interactions are often the product of coevolution. 2. Classify population interactions in terms of the positive and negative effects that the interactions have on the interacting populations. 3. Compare the species diversity of different ecological communities on the basis of their species richness and the Three interacting populations. Ladybird relative abundances of species within them. beetles (Coccinella septempunctata) feed on aphids (order Hemiptera), which consume the sap of plants. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Predation and Herbivory Predation (interaction between predators and their animal prey) and herbivory (interaction between herbivores and the plants they eat) are important in ecological communities. Both predators and herbivores have evolved specialized behaviors and anatomical structures that help them obtain and consume food. Some species (specialists) feed on one or few types of food – other species (generalists) eat a wide variety of food. https://slideplayer.com/9316246/28/images/slide_1.jpg https://cdn-acgla.nitrocdn.com/bvIhcJyiWKFqlMsfAAXRLitDZjWdRlLX/assets/static/optimized/rev-5131b73/wp-content/uploads/2016/10/ Cheetah_hunting_springbok.jpg Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Defenses Against Herbivory Plants and animals have evolved mechanisms that reduce the probability of being eaten These include: Protective spines or thorns Tough epidermis Poisonous chemicals Camouflage Warning coloration https://textimgs.s3.amazonaws.com/boundless-biology/acacia-collinsii.jpe Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Active Defenses Against Predation Passive Defenses Against Predation North American porcupines release sharp, barbed Mimics that look like something unappetizing quills that stick in a predator’s mouth, causing can hide in plain sight (e.g., caterpillars that look severe pain. like bird droppings). Other species fight back by biting, charging, or Cryptic coloration helps some prey (and some kicking an attacking predator. predators) to blend in with their surroundings. Some produce chemical defenses (e.g., skunk A cornered prey may try to startle or intimidate spray; neurotoxic skin secretions in some frogs and toads). the predator with a display that increases their apparent size or ferocity. Some insects protect themselves with poisons acquired from plants (e.g., monarch caterpillars and Some species hide in a protected site. milkweed toxins). FIGUUR 53.3 Skuil in die oog. Sommige diere, soos (A) https://encrypted- https://varmentguard.com/ reuse-swaelstert-vlinderlarwes wat soos voëlmis lyk en (B) tbn0.gstatic.com/images? q=tbn:ANd9GcTG7ywqB40LtDdr uploads/blog/913f054d-10cb-4516- b295-cd669dc44938/skunk- sommige sprinkane wat soos dooie, insekbeskadigde RpBFWCOpWm0hpJ4Nj2t- spray.jpg blare lyk, trek nie die aandag van roofdiere nie. Hg&usqp=CAU Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Cryptic Colouration Ibex Dead-leaf moth Lizard  Aposematic Coloration Poisonous or noxious species often advertise with bright, contrasting patterns (aposematic coloration). Examples: A black-and-white skunk, a yellow-banded wasp, or an orange monarch butterfly. A predator quickly learns to associate the color pattern with pain, illness, or severe indigestion – and rarely attacks these easily-recognized animals again. FIGURE 53.5 Aposematic coloration. Poisonous animals, such as this poison dart frog (Ranitomeya ventrimaculata) from the Amazon basin, often have bright warning coloration. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Mimicry Mimicry, in which one species evolves an appearance resembling that of another. In Batesian mimicry, a harmless species (the mimic) resembles an unpalatable or poisonous one (the model). In Müllerian mimicry, two or more unpalatable species share a similar appearance, which reinforces the lesson learned by a predator that attacks any species in the mimicry complex. Figure 53.6 Mimicry. (A) Batesian mimics are harmless animals that mimic a dangerous one. The newly hatched chicks of the cinereous mourner (a bird) is a Batesian mimic of the poisonous caterpillars of flannel moths. The chicks even wriggle the way the caterpillars do. (B) Müllerian mimics are poisonous species that share a similar appearance. Two distantly related species of butterfly, have nearly identical patterns on their wings. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Interspecific Competition Interspecific competition (competition between species) occurs when populations of different species use the same limiting resources. Competing populations may experience increased mortality and decreased reproduction – similar to the effects of intraspecific competition. Interspecific competition reduces the size and population growth rate of one or more of the competing populations. In interference competition, individuals of one species harm individuals https://upload.wikimedia.org/wikipedia/commons/7/7f/Panthera_leo_%26_Crocuta_cro of another species directly: Animals may fight for access to resources; Plant species may release toxic chemicals that prevent other plants from growing nearby. In exploitative competition, two or more populations use (“exploit”) the same limiting resource: The presence of one species reduces resource availability for the others – in the absence of direct confrontations. https://i.ytimg.com/vi/rl6MhqywDpI/maxresdefault.jpg Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Gause’s Experiments G. F. Gause grew cultures of two Paramecium species that fed on the same bacteria suspended in the culture medium: When grown alone, each species exhibited logistic growth; When grown together in the same dish, Paramecium aurelia persisted at high density, but Paramecium caudatum was nearly eliminated. Gause called this effect competitive exclusion. Gause’s competitive exclusion principle states that populations of two or more species that rely on the same limiting resources and exploit them in the same way cannot coexist indefinitely. One species is inevitably more successful, harvesting resources more efficiently and producing more offspring than the other. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  The Niche Concept A population’s ecological niche is defined by the resources it uses and the environmental conditions it requires – including food, shelter, nutrients, light intensity, and temperature. A population’s fundamental niche includes all conditions and resources it can possibly use – its realized niche is the range of conditions and resources it actually uses. Competition between two populations can be visualized by plotting their fundamental and realized niches with respect to one or more resources. A number of species may occupy a particular habitat, but their niches differ to avoid competition No two species in a community can occupy exactly the same niche. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Resource Partitioning One way populations reduce competition in nature is by resource partitioning – the use of different resources, or the use of resources in different ways, by species living in the same place: Example: Weedy plants avoid competition for water and dissolved nutrients in abandoned fields by collecting them from different depths in the soil. Jim Thomas; Emilio100/Shutterstock.com; samray/Shutterstock.com In the coastal habitat in Florida there are a number of wading birds, each with a unique niche Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  The classic experimental demonstration of competition in the field was done by Joseph Realised niche Connell (1961a, 1961b). Control: No treatment. Chthamalus Fundamental niche occupies only shallow water and Balanus occupies only deep water. Treatment 1: Remove Balanus. In the absence of Balanus, Chthamalus occupies both shallow water and deep water. Treatment 2: Remove Chthamalus. In the absence of Chthamalus, Balanus still occupies only deep water. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Character Displacement A second way populations reduce competition in nature is by character displacement: when a particular character is more divergent (different) when two populations belong to the same community than when they do not. Sympatric populations (living in the same place) are morphologically different and use different resources. Allopatric populations (living in different places) are morphologically similar and use similar resources; Seed eating ground finches. When the two species occur on separate islands, their beaks are of a similar depth. When species co-occur on the same island, their beaks differ. This reduces competition. Beak depth corresponds to the size of seed the bird eats. Stubblefield Photography/Shutterstock.com; Natursports/Dreamstime.com Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Symbiotic Associations Biologists define three types of symbiosis (associations between species) that differ in their effects: In commensalism, one species benefits and the other is unaffected (e.g., cattle and cattle egrets) – rare in nature; In mutualism, both partners benefit (e.g., yucca and yucca moth) – extremely common in nature; In parasitism, one species (the parasite) uses another (the host) in a way that is harmful to the host. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Mutualism between Plants and Animals  A symbiotic relationship in which both members benefit  Mutualistic relationships need not be equally beneficial to both species  Organisms often help each other obtain food or avoid predation  Common in all kingdoms of life (A) Douglas Knight/Shutterstock.com; (B) Harlo H. Hadow; (C) Harlo H. Hadow Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Mutualism 1. Facultative  Both species benefit from the interaction, but can live without each other  E.g. Cleaner wrasse 2. Obligate  Neither of the species can survive without the other  E.g. scanned,Some pollinators Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Examples of Mutualism  Rhizobia (nitrogen- fixing bacteria) live in nodules on the roots of legumes  Convert atmospheric nitrogen into a form the plant can use  In return the plant supplies the bacteria with carbohydrates, Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Commensalism 322554823/figure/fig13/AS:668815515979787@1536469453835/Ficus- Symbiotic relationship in which https://www.researchgate.net/profile/Richard-Riefner-Jr/publication/ microcarpa-a-strangler-fig-is-epiphytic-on-a-palm-tree-trunk-with- one species benefits and the other neither benefits nor is https://www.sharktrust.org/GetImage.aspx?IDMF=5ac62756-04b2-4abf-b727-ced762bf131b&w=1949&h=1230&src=mc harmed Examples: Nephrolepis_W640.jpg Epiphytes grow in the branches of trees, where they receive more light, but take no nourishment from the tree. Remora fish attach themselves to sharks and eat their leftover food; The sharks are not affected by this. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Parasites and Parasitoids Tapeworms and other parasites that live within a host are endoparasites – endoparasites generally complete their life cycle in one or two host individuals. Leeches and other parasites that feed on the exterior of a host are ectoparasites – most animal ectoparasites have elaborate sensory and behavioral mechanisms. Parasitoids are insects that lay eggs in the larva or pupa of another insect species, and her young consumes the tissues of the living host. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Population Interactions and Effects TABLE 53.1 Population Interactions and Their Effects Interaction Effects on Interacting Populations Predation +/- Predators gain nutrients and energy; prey are killed or injured. Herbivory +/- Herbivores gain nutrients and energy; plants are killed or injured. Parasitism +/- Parasites gain nutrients and energy; hosts are killed or injured. Competition -/- Both competing populations lose access to some resources. Commensalism +/0 One population benefits; the other population is unaffected. Mutualism +/+ Both populations benefit. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  53.2 The Nature of Ecological Communities Community structure changes as a result of interactions between populations These interactions include: Competition Predation Parasitism Commensalism Mutualism Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Species Richness Communities differ greatly in the number of species that live within them (species richness). Composition is a listing of various species in the community. Diversity includes both species richness (i.e. composition) and species abundance (eveness). Within every community, populations differ in relative abundance of individuals. Some communities have just one or two dominant species that represent a majority of the individuals present, and some rare species represented by just a few individuals. In other communities, species are represented by more equal numbers of individuals. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Foundation Species In many ecological communities, one species acts as a foundation species, defining the nature of a community by creating locally stable environmental conditions: Example: Saltmarsh cordgrass (Spartina) is a foundation species on Salt marshes in South Africa. A keystone species is a species that plays a greater role in a maintaining the function and diversity of a community than would be predicted by their abundance. The removal of a keystone species can have disastrous consequences for the entire community. Example: African elephant Prevents bush encroachment by feeding on shrubs and small trees, thereby maintaining the habitat as open grassland. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Transition Zones Broad transition zones (ecotones) between adjacent communities include species from both neighboring communities – and some species that thrive only in transitional conditions. In some places, however, discontinuity in a critical resource or an important abiotic factor produces a sharp community boundary. The growth forms of plants (sizes and shapes) vary markedly in different environments. Warm, moist environments support complex vegetation with multiple vertical layers (e.g., tropical forests). Physically harsh environments (e.g., mountaintops) are occupied by low vegetation with simple structure. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Trophic Structure The trophic structure of a community is a hierarchy of trophic levels, defined by the feeding relationships among its species. First trophic level (primary producers or autotrophs): Plants and other photosynthetic organisms that capture sunlight and convert it into chemical energy; Animals are consumers (heterotrophs) – they acquire energy and nutrients by eating other organisms or their remains: Second trophic level (primary consumers): Herbivores that eat plants; Third trophic level (secondary consumers): Carnivores that feed on herbivores; Fourth trophic level (tertiary consumers): Carnivores that feed on other carnivores. Some organisms, including humans and some bears, are omnivores, feeding at several trophic levels simultaneously. Scavengers (detritivores) are animals that ingest dead organisms, digestive wastes, and cast-off body parts such as leaves and exoskeletons (e.g., earthworms and vultures). Decomposers are small organisms, such as bacteria and fungi, that feed on dead or dying organic material. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Food Chains and Webs The trophic structure of a community is a food chain in which one organism eats another – each link in the chain points from the food to the consumer. Straight-line food chains are rare in nature – most consumers feed on more than one type of food, and most organisms are eaten by more than one type of consumer. These complex relationships are portrayed as a food web – a set of interconnected food chains with multiple links. When environmental disturbances eliminate some species, links between trophic levels contribute to community stability. In species-rich communities, loss of one or two species has only minor effects on the stability of the community as a whole. Regardless of species richness, a community includes two to three prey species for every predator species. Trophic cascade, an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations https://res.cloudinary.com/dtpgi0zck/video/upload/q_auto/vc_vp9/v1/videos/ Wolves%20of%20Yellowstone.webm?_s=vp-1.9.1 https://upload.wikimedia.org/wikipedia/ commons/thumb/d/d6/Trophic_Cascade_1.svg/ https://www.youtube.com/watch?v=b9xVEeYAs3w 200px-Trophic_Cascade_1.svg.png Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Ecosystems An ecosystem is a biological community and the physical environment with which there is a flow of energy between different components. Ecosystem ecology is the branch of ecology that analyzes the flow of energy and the cycling of materials between an ecosystem’s living and nonliving components. These processes make the resident organisms highly dependent on each other and on their physical surroundings. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Primary Productivity The rate at which producers convert solar energy to chemical energy is an ecosystem’s gross primary productivity. After deducting the energy producers use for their own maintenance (cellular respiration), the remaining chemical energy is the ecosystem’s net primary productivity. Primary productivity is measured in units of energy captured (kcal/m2/yr) or in units of biomass created (g/m2/yr). Biomass is the dry weight of biological material per unit area or volume of habitat. Standing crop biomass is the total dry weight of plants present at a given time. Net primary productivity is the rate at which the standing crop produces new biomass. Ecologists usually measure changes in biomass to estimate productivity. The rate of photosynthesis in an ecosystem is proportional to the intensity and the duration of sunlight, which vary geographically and seasonally. In every ecosystem, one nutrient inevitably runs out before the others – the element in short supply is called a limiting nutrient because its absence limits productivity. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  The Carbon Cycle (2 of 5) Carbon atoms are the backbone of most biological molecules. In photosynthesis, producers convert atmospheric carbon dioxide (CO2) into carbohydrates. Heterotrophs acquire carbon by eating other organisms or detritus. Carbon moves in the sea and on land – atmospheric CO2 creates a global carbon cycle. The largest reservoir of unavailable inorganic carbon is sedimentary rock, such as limestone or marble. Most available carbon is present as dissolved bicarbonate ions (HCO3− ) in the ocean. Soil, atmospheric CO2, and plant biomass form other significant, reservoirs of available carbon. Some marine organisms incorporate dissolved calcium into calcium carbonate (CaCO3) shells that sink to the bottom and remain buried in sediments for millions of years (as sedimentary rocks). Carbon atoms were also transferred to the unavailable organic compartment when soft-bodied organisms were converted to gas, petroleum, or coal – which humans now use as fossil fuels. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  54.4 Human Activities and Anthropogenic Global Change Human activities such as industrial, agricultural practices, and development disrupt biogeochemical cycles by moving materials from one nutrient compartment to another at unnaturally rapid rates. The combustion of fossil fuels (oil, coal, and peat) and wood is transferring carbon from organic nutrient reservoirs to the atmosphere at an unprecedented rate. Molecules of CO2, water, ozone, methane, nitrous oxide, and other greenhouse gases impede the escape of energy into space, trapping much of that energy as heat. The natural accumulation of heat in the lower atmosphere (greenhouse effect) prevents Earth from being a cold and lifeless planet. Scientists estimate that atmospheric CO2 concentration has increased 35% in the last 150 years and 16% in the last 30 years. Although more than half the CO2 emissions are absorbed by forests and marine phytoplankton, vast tracts of tropical forests are being cleared and burned, reducing the biosphere’s capacity to maintain the carbon cycle. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Changes in the Global Carbon Cycle are Warming the Earth Rising CO2 levels in the atmosphere and in oceans have many https://nationalmuseumpublications.co.za/wp-content/uploads/2020/03/web-main-web01.png consequences, including acidification of aquatic ecosystems and intensifying the greenhouse effect. The greenhouse effect contributes to global warming – mean temperature of the lower atmosphere will rise 2.0° to 6.5°C during the 21st century. Increased temperature leads to melting glaciers, rising sea levels, and changes in regional patterns of precipitation and temperature. Changes in geographical distributions of many organisms in response to modest levels of global warming (0.7°C in the 20th century). Aloidendron dichotomum Rising sea levels could inundate low coastal regions, including cities and agricultural areas. What is the main biome in Bloemfontein (Free state)? What is the climate like in Bloemfontein? How will climate change in Bloemfontein? Which Biome will become dominant in Bloemfontein with climate change? Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Biodiversity Biodiversity is the richness of living systems. Biodiversity is described at three levels: Genetic variation: the raw material for adaptation, speciation, and evolutionary diversification; Species richness: the number and variety of species within a community – influences its overall characteristics, population interactions, and trophic structure; Ecosystem level: complex interactions bind species in an ecosystem http://www.biodiversitybc.org/assets/Taking~Natures~Pulse/figure-2 together – different ecosystems interact within the biosphere. Biodiversity is declining dramatically, perhaps faster than ever before in Earth’s history. Three broad threats are caused by humans and exacerbated by global climate change: Clearing of forests (deforestation and desertification); Commercial overexploitation of marine fish populations; Hydrologic alterations of freshwater ecosystems. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Deforestation Global deforestation occurs at a rate of 5.6 mil hectares per year – 15,000 ha per day. More than 90% of deforestation occurs in tropical regions, where many organisms exhibit their highest diversity. Forests are most often cut to clear land for grazing livestock. Brazil, which contains 27% of the planet’s aboveground woody biomass, accounts for 25% of all deforestation. Most tropical forests are burned as they are cleared, which adds CO2 to the atmosphere, enhancing the greenhouse effect and increasing the rate of global warming. Forest cutting now contributes nearly 20% of all greenhouse gases released into the atmosphere. Deforestation also reduces the amount of carbon (CO2) removed from the atmosphere by photosynthesis. Once a forest is cut, heavy grazing or farming drains nutrients from the soil, requiring the application of fertilizers. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Desertification When large tracts of subtropical forest are cleared and overused, the land often undergoes desertification: Groundwater table recedes to deeper levels; Less surface water is available for plants; Soil accumulates high concentrations of salts (salinization); Topsoil is eroded by wind and water. Desertification speeds up the loss of biodiversity locally. Desertification has decimated habitats in the Sahel region of Africa. Excessive grazing of cattle and goats by an expanding human population is the main reason for the Sahara’s southward expansion at a rate of 5.5 to 8 km per year. Because sand dunes of the expanding desert shift constantly, agriculture and grazing are nearly impossible, resulting in frequent famines. Due to construction of drainage canals and excessive withdrawal of groundwater. Deforestation, desertification, and global warming reinforce each other in a positive feedback cycle. If deforestation and desertification continue, we will soon lose a large proportion of Earth’s forests and face a decrease in the area of habitable land. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Overexploitation Excessive harvesting of an animal or plant species (overexploitation) can cause evolutionary changes and local extinctions. Today, overexploitation severely threatens marine ecosystems – the only environment from which we routinely harvest predators (such as tuna) as food. Because of overfishing, the average yield of the Grand Banks has declined to less than 10% of the highest historic levels. Fish populations have decreased to dangerously low levels, and the fishing industry itself is imperilled around the world. Reports estimate that modern fishing techniques have reduced the biomass of large predatory fishes by about 90% in marine ecosystems. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Hydrologic Alterations Hydrologic alterations are changes to the pathways through which water moves in the hydrologic cycle. Water from these reservoirs is distributed for agricultural, industrial, and domestic uses, used to generate hydroelectric power, and used to control water flow to mitigate flooding. These hydrologic alterations have made freshwater ecosystems among the most endangered on Earth. Damming of rivers and the diversion of their flow threaten freshwater biodiversity in four ways: Flow rate and volume are key determinants of river habitats – a major influence on organisms that live there; Life histories of aquatic species, evolved in response to natural flow patterns, are disrupted by changes in flows; Dams reduce a river system’s “connectivity” – preventing fishes from migrating freely through a river system; Dams and reservoirs facilitate introduction of non-native species that thrive in disturbed habitats. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  55.2 Specific Threats to Biodiversity When humans colonize a habitat, they reduce areas of intact habitat to small, isolated patches (habitat fragmentation). Small habitat patches can sustain only small populations of organisms (low carrying capacities). Isolated populations are often separated by an unsuitable habitat that organisms do not cross – reducing gene flow. The combination of small population size and genetic isolation reduces genetic variability and fosters extinction. The borders of fragmented habitats are exposed to edge effects such as additional sunlight, wind, rainfall – and noise and pollution from human activities. Example: Scott K. Robinson found that three factors decrease populations of migratory songbirds in fragmented habitats: Small forest patches often lack specific habitat types that songbird species require; Songbirds breeding in forest patches are more likely to suffer from brood parasitism; Nests in forest patches experience increased predation. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Pollution Pollutants are materials or energy in forms or quantities that organisms do not usually encounter. Chemical pollutants, the by-products or waste products of agriculture and industry, are released locally – but many spread in water or air on a continental or global scale. Example: Sulfur dioxide (SO2) from coal-burning power plants dissolves in water vapor and forms sulfuric acid, which falls as acid precipitation, acidifying soil and bodies of water. Air pollution: Wastes produced by the combustion of fossil fuels in factories and automobile engines produce pollutants that increase rates of asthma and other respiratory ailments. Water pollution: The 2010 Deepwater Horizon oil rig spill in the Gulf of Mexico originated locally but had a broad impact on organisms in the Gulf and adjacent wetlands. Terrestrial pollution: All vulture species in South Asia are now on the verge of extinction due to eating carcasses of livestock treated with the anti-inflammatory drug diclofenac. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Introduction of Invasive Species The introduction of nonnative organisms (exotic species) into new habitats poses a serious threat to biodiversity. Exotic species often prey upon, parasitize, or outcompete native species, leading to their extinction. Black Wattle is Acacia mearnsii Many have r-selected life histories – they mature and reproduce quickly and thrive in degraded habitats. In South Africa 19 species were assessed by Acacia cyclops rooikrans experts as having severe impacts were terrestrial plants (16 species). Triffid Weed (Chromolaena odor Included seven species of Australian trees and shrubs in the genus Acacia. Acacias have been implicated in reducing grazing potential and surface water Mesquite trees (Prosopis spp.) runoff, and biodiversity. Lantana (Lantana camara Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Spread of Disease-Causing Organisms Exotic species may carry pathogens that devastate populations that never developed immunity to them: Example: Scientists attribute recent world-wide extinctions and declines in more than 200 amphibian species to infection by the chytrid fungus Batrachochytrium dendrobatidis. The infection originated in African clawed frogs that were exported to many countries for use in biological research and for the pet trade. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Chytrid Fungus Infection Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  An Increase in Extinction Rates Background extinction rate refers to the normal extinction rate before humans became a primary contributor to extinctions. These are species that go extinct simply because not all life can be sustained on Earth and some species simply cannot survive. At least six mass extinctions, during which extinction rates increased greatly above the background rate for short periods of geological time, appear in the fossil record. The greatest mass extinction of all time is occurring now, with extinction rates 1,000 times the historical background rate. Thousands of species are being driven to extinction each year as direct result of human activities and population growth. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  55.3 Ecosystem Services That Biodiversity Provides Human activities are causing the current dramatic decline in biodiversity. Three types of ecosystem services: Provisioning services. Regulating and support services. Cultural services. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Provisioning Services Benefit Humans Directly Crop agriculture using indigenous South African species Rooibos (Aspalathus linearis) is indigenous to South Africa’ s Fynbos biome and makes a caffeine-free tea. Has become very popular globally because of its various health benefits. While the ‘Nortier’ variety is now widely grown by commercial farmers and is the most commonly consumed rooibos, wild rooibos is more genetically diverse and drought-resistant.. https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTtcO1B_ueRMmJvM5de2lXI-Clf9rKeNJbtSQ&us Honeybush is another caffeine-free hot beverage, made from a number of species from the genus Cyclopia (also indigenous to South Africa’s Fynbos biome). Unlike Rooibos, honeybush has enjoyed limited commercial interest and most biomass is still harvested https://afrigetics.com/product-category/botanicals/honeybush-tea/ from the wild. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Medicinal plants Many South Africans depend heavily on wild indigenous plant species for health care. There are 2 062 (10.1% of national flora) plant species used for medicine in the country. The informal trade of medicinal plant species is 40 885 tonnes of raw material from the wild. The value of the African Traditional Medicine (ATM) industry is estimated to be approximately R17.96 billion per year. https://cms.groupeditors.com/img/fr_2017830162353.jpeg It is estimated that 70-72% of South Africa’s population use ATM. As South Africa has an average of only 64 allopathic doctors per 100 000 lives (the world average is 152). The use of ATM and the related dependence on medicinal plant material is very high. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Regulating and Support Services Benefit All Forms of Life Flood attenuation Riparian buffers and wetlands can slow runoff and absorb excess water during flood events. This reduces peak flows and can lessen downstream flooding. The contribution that wetlands make to flood attenuation has been well in South Africa. declining extent of wetland down to approximately 1/3 of the 1950s extent there was a For the Kromme River wetland, showed a corresponding declining contribution to flood attenuation by approximately 1/3 of its original extent. http://pza.sanbi.org/sites/default/files/images/plants/10820/prio Wetlands located low in the catchment have a greater potential to reduce floods than headwater wetlands. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  https://eturbonews.com/wp-content/uploads/2019/10/south-africa-tourism-810x5 Biodiversity-based tourism is contributing substantially to economic growth Tourism contributes considerably to the South African economy. While domestic tourism tends to fluctuate, currently decreasing due to economic constraints and ‘belt-tightening’ by South African citizens. Foreign tourism to South Africa is increasing. Tourism’s total impact on the South African https://www.planetware.com/photos-large/SAF/south-africa-cape-town.jpg economy ranges around 9.3% of Gross Domestic Product, and nearly 10% of all employment opportunities in South Africa are to some extent influenced by the tourism sector. Approximately 45% of tourists are from the Americas and Europe already participate in these key activities or attractions. While visitors from other African countries largely do not participate in the country’s wealth of biodiversity assets. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, https://encrypted-tbn2.gstatic.com/images? or posted to a publicly accessible website, in whole or in part. q=tbn:ANd9GcQLYNgQ6s0ItHqSZIk_EdDxvstWoRoiAv1hCRo8ZI-aIw98n275  Cultural Services Reflect Intrinsic Worth https://encrypted-tbn0.gstatic.com/ Ethicists argue that biodiversity has intrinsic worth as living species, independent of direct or indirect value to humans. http://www.lifeofmike.co.za/wp-content/uploads/2017/02/Hole-in-the-Wall-17-1.jpg Countering this position is the view that human needs should always rank above those of other species and that we should use them to maximize our own welfare. images? This debate deals more with philosophy and public policy than biology – Hogsba nevertheless, many people feel that the natural landscape enhances human ck existence in intangible ways. Special places in South Africa also have spiritual and cultural significance. Including the Motouleng caves (meaning 'place of beating drums') located in the mountains of the eastern Free State and Lesotho, which have served as a spiritual Mpako River gathering place of prayer for over 800 years. https://upload.wikimedia.org/wikipedia/ Hogsback in the Eastern Cape is regarded as a place of spiritual upliftment. Xhosa legend holds that the Hole in the Wall landmark at the mouth of the Mpako River is the gateway to the world of their ancestors. Even in urban areas, there are natural spaces popular for rituals and prayer. Lion’s Head in Cape Town, Melville Koppies in Johannesburg. Lion’s Head in Cape T Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  Benefits of Biodiversity in the Terrestrial Realm Biodiversity enriches everyday lives Biodiversity citizen scientist is another way that people feel connected to South Africa’s biodiversity and enriched in their everyday lives. SANBI and various other institutions in the sector have long recognised the value of citizen science and several projects. Platforms have emerged to help channel the South African public’s interest and passion for biodiversity conservation into providing vital assistance to biodiversity science. iNaturalist and the Southern African Bird Atlas Project (SABAP) are used by scientists to support various biodiversity monitoring projects as the data feeds into national databases of species distribution records. Transcribe system, which enables citizen scientists to contribute and digitise the many historical museum, herbaria and field note records archived in collections. This digitising provides vital historical information about species distributions and field trips undertaken up to 300 years ago. Russell, Biology: The Dynamic Science, 5th edition. © 2021 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.