BLGY1643: Ecology and the Biosphere Lecture Notes PDF

BLGY1643 The interdependence of plants and life on earth. Dr Dimitri Veldkornet Email: [email protected] Office: 238 Biology Building Tel nr: 051 401 2928  Module information Theme 4 Biodiversity and Ecology (Dr D.A. Veldkornet) Chapter: 51, 53, 54 & 55 Te...

BLGY1643 The interdependence of plants and life on earth. Dr Dimitri Veldkornet Email: [email protected] Office: 238 Biology Building Tel nr: 051 401 2928  Module information Theme 4 Biodiversity and Ecology (Dr D.A. Veldkornet) Chapter: 51, 53, 54 & 55 Textbook/ - Biology, the Dynamic Science. 4th or 5th Edition (2015), Russel, Hertz & McMillan (Cengage Learning). Lecture 13: Ecology and the Biosphere (Chapter 51: p 1151- 1178) Lecture 14: Population Ecology (Chapter 52: p 1179 - 1206) Lecture 15: Population Interactions and Community Ecology (Chapter 53: p 1207 – 1236) Lecture 16: Ecosystems, Biodiversity and Conservation (Chapter 54 and 55: p 1237 - 1288) INTRODUCTION TO ECOLOGY  Learning Objectives 1. Describe the hierarchical levels at which ecologists conduct research. 2. Illustrate how the Earth’s shape, tilt on its axis, and its rotation around the sun establish major weather patterns. 3. Relate the climate where you live to worldwide, regional, and local geographical features. 4. Formulate a hypothesis about how climate change will influence the distributions of species and their reproductive schedules in the region where you live. 5. Provide evidence to support the idea that the distributions of terrestrial biomes are in large product of global, regional, and local weather regimes. 6. Predict which terrestrial biome(s) is (are) likely to occur under a given set of environmental conditions. 7. Describe the environmental differences between streams, rivers, and lakes. 8. Compare the environments in neritic, oceanic, and abyssal zone of the oceans.  Origins of Ecology Ecology is the study of interactions between organisms and their  “Ecology” coined in 1870 by German zoologist Ernst environments. Haeckel.  From Greek oikos (home) and All environments have both biotic logy (study of).  May be thought of as the study (living/biological) and abiotic of the “home life” of organisms (non-living/nonbiological) components. Haekel did little more than name the discipline. The biotic environment includes all organisms found in a particular place. The abiotic environment includes temperature, moisture, soil chemistry, and other physical 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.  Levels of Organization Organismal ecologists study the genetic, biochemical, physiological, morphological, and behavioral adaptations of organisms to the abiotic environment. Population ecologists study how the size and other characteristics of populations (groups of individuals of the same species that live together) change in space and time. Community ecologists study interactions between species – how predation, competition, and environment influence community development, organization, and structure. Ecologists studying ecosystem ecology explore the cycling of nutrients and flow of energy between biotic components of an ecological community and the abiotic environment. The largest-scale ecological studies focus on the biosphere. 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.  51.1 The Science of Ecology The major research questions of basic ecology relate to the distribution and abundance of species and how they interact with each other and with the physical environment. Using these data, workers in applied ecology develop conservation plans and amelioration programs to limit, repair, and mitigate ecological damage caused by human activities. 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.  How do we study Ecology?  Observation You want to explain a certain aspect of the natural world. Hypothesis  Based on your observations, you construct a hypothesis.  Experiments  You conduct experiments to test the hypothesis.  Conducting Experiments The study on trophic cascades involving wolves in Yellowstone National Park: Population Ecology: The study tracks the impact of wolves on the population sizes, dynamics, and behaviour of other species, particularly herbivores like elk and deer. Community Ecology: Investigating the interactions between species (wolves, deer, plants, beavers, etc.) and how changes in one species (wolves) affect the structure and dynamics of the entire community. Ecosystem Ecology: Examining the transfer of energy and nutrients through the food web and how top predators (wolves) influence lower trophic levels, including herbivores (deer) and producers (plants). Restoration Ecology: As the study looked at the effects of reintroducing a species (wolves) to restore ecological balance and biodiversity, it's also an example of research on the effects of human intervention on ecosystems. Landscape Ecology: The study addresses changes in the physical environment (such as river stabilization) that result from biological interactions, showing how species interactions can influence physical landscapes. 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.  52.1 What is a population? A population is a group of individuals of a single species that live in a particular area and interact with one another. 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.  52.1 Population Characteristics Population dynamics/Demography describes how the characteristics of populations change through time and vary from place to place. Population size is the number of individuals in a population at a specified time. Population density is the number of individuals per unit area or per unit volume of habitat. A population’s density provides information about its relationship to the resources it uses. Species with large body sizes generally have lower population densities than species with smaller body sizes Every population has a geographical range, the overall spatial boundaries within which it lives. Every population occupies a habitat, a specific environment characterized by its biotic and abiotic features. 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.  Estimating Population Size and Density For large-bodied species, a simple head count provides accurate information. For tiny organisms that live at high population densities, such as aquatic https://images.thefishsite.com/fish/legacy/files/articles/old/12-12-1 phytoplankton, population size can be extrapolated from counts of water samples. In other cases, researchers use the mark- release-recapture sampling technique. Michael C. Singer, University of Texas 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 Distribution Populations vary in their dispersion, the spatial distribution of individuals within the geographical range. In random dispersion, individuals are distributed unpredictably within a uniform habitat. In clumped dispersion, individuals group together due to patchy habitats, social groups, or reproductive patterns. In uniform dispersion, individuals repel each other and tend to be evenly spaced because resources are in short supply. 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.  Age Structure Age structure is a statistical description of the relative numbers of individuals in each age class. Individuals can be generally categorized as prereproductive, reproductive, or postreproductive. A population’s age structure reflects its recent growth history and predicts its future growth potential. Populations that include many prereproductive will continue to grow larger as young individuals mature and reproduce. Generation time is the average time between the birth of an organism and the birth of its offspring. Generation time is usually short in species that reach sexual maturity at a small body size – their populations grow rapidly because of rapid accumulation of reproductive individuals. Sex ratio is the relative proportions of males and females – generally, the number of females in a population has a bigger impact on population growth than the number of males. Parameter Value Average lifespan in Yellowstone 4-5 years Proportion of population >5 years old 18% Average pack size in Yellowstone 9.8 Sex ratio 50:50 Average litter size at den emergence 4.4 pups Average number Russell, of pups surviving Biology: The Dynamic Science,3.2 5th edition. pups© 2021 Cengage. All Rights Reserved. May not be until December scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.  52.2 Demography Demography is the statistical study of the processes that change a population’s size and density through time. Populations grow through the birth of individuals and the immigration (movement into the population) of organisms from neighbouring populations. Death and emigration (movement out of the population) reduce population size. A life table summarizes the demographic characteristics of a population. To collect life-table data for short-lived organisms, demographers mark a cohort of individuals of similar age and monitor them until all members of the cohort die. A cohort, is a group of individuals of the same species, in the same population, born at the same time. For organisms that live more than a few years, a researcher might sample the population for one or two years and extrapolate the results over the species’ life span. Age-specific mortality is the proportion of individuals alive at the start of an age interval that died during that age interval. Age-specific survivorship is the proportion of individuals alive at the start of an age interval that survived until the start of the next age interval. 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.  Life Tables Life tables summarize the proportion of the cohort that survived to a particular age – a statistic that identifies the probability that any randomly selected newborn will still be alive at that age. Life tables also include data on age-specific fecundity, the average number of offspring produced by surviving females during each age interval. TABLE 52.1 Cohort of 843 individuals of Poa annua (Annual Bluegrass) Age Interval (in Number Alive at Start of Age Number Dying during Age Age-Specific months) Interval Interval Mortality Rate 0–3 843 121 0.144 3–6 722 195 0.270 6–9 527 211 0.400 9–12 316 172 0.544 12–15 144a 90 0.625 15–18 54 39 0.722 18–21 15 12 0.800 21–24 3 3 1.000 24– 0 — — 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.  Survivorship Curves A survivorship curve shows the rate of survival for individuals over the species’ average life span. Type I curves reflect high survivorship until late in life – typical of large animals that produce few young. Type II curves show a constant rate of mortality in all age classes – seen in small animals subject to predation. Type III curves reflect high juvenile mortality, followed by a period of low mortality once offspring reach a critical size. 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.  52.3 The Evolution of Life Histories Life histories describe the lifetime patterns of growth, maturation, and reproduction of an organism. Every organism is constrained by an energy budget – the total amount of energy it can accumulate to fuel its activities. Excess energy is stored as starch, glycogen, or fat. Organisms use energy for three general functions: growth, maintenance, and reproduction. Ecologists also consider the age at which the organism first reproduces. Early reproducers increase their chance of leaving some surviving offspring, but the energy devoted to reproduction is no longer available for maintenance and growth. An individual that delays reproduction may increase its chance of survival and its future fecundity, but there is always a chance it will die before breeding, leaving no offspring at all. Single vs. multiple reproductive events: Those who can reproduce only once (semelparity) Those who can reproduce several times over their lifetime (iteroparity) 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.  52.4 Models of Population Growth Mathematical models of population growth describe different responses to changes in a population’s density. Geometric and exponential models apply when populations experience unlimited growth. Bacteria reproduce by binary fission – if no bacteria die, the population doubles in size each generation; Generation time is the time between successive cell divisions – as short as 20 minutes. Population size increases steadily by a constant ratio; A graph of exponential population growth has a characteristic J shape, getting steeper through time. 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.  Exponential population growth In plants and animals, new organisms (births) increase a population's size and mortality decreases it. ΔN/Δt = B – D ΔN The change in population size Δt is the period during which the change occurs B Is the Number of Births D the number of deaths during period 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. Change in population size The per capita (b) birth rate is the number of births in the population during the specified period divided by population size: b = (B/N). The per capita mortality rate (d) is the number of deaths divided by population size: d = (D/N). Birth and death rates per capita are averaged across all individuals in the population – and expressed over a defined period of time (calculated from data in a life table). The change in a population's size during a given period (ΔN/Δt) depends on the per capita birth and death rates, as well as on the number of individuals in the population. (ΔN/Δt) = (b – d)N This comparison describes the exponential model of population growth. The difference between b and d (b – d) is the population’s per capita growth rate ®– expressed per individual per unit of time. Using the per capita growth rate, r, the exponential growth equation is written: dN / dt = rN. If (r > 0), the population grows; if (r < 0), the population becomes smaller; and if (r = 0), the population's size changes not. 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.  Logistics Growth For exponential growth to continue unchecked, there must be unlimited resources available for the population. In reality, this is seldom the case Shortages of food and shelter, increased competition between individuals and disease outbreaks, will eventually cause growth to slow down. Logistic growth results when the environment restricts growth and usually occurs in organisms with continuous breeding. Four phases: Birth < or = Death lag phase - Growth is slow, as the population is still small deceleration growth phase 1. Exponential growth phase – Growth increases as more Population size individuals are added Equilibrium phase 2. Decreasing growth phase– Growth slows down Birth > Death 3. Equilibrium phase– Very little growth Birth = Death Lag phase Exponential growth phase Generations 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.  Carrying capacity The carrying capacity (K) of a population is the maximum number of individuals that can be supported by the environment. Population growth cannot increase indefinitely because resources are limited. When a population reaches carrying capacity, it stops growing – the death rate corresponds to the birth rate. The population will usually vary around the carrying capacity. Carrying capacity Population size Generations 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.  Logistical Growth A formula including carrying capacity should be used to calculate logistical population r=1 growth K= 10 The formula becomes: G = rmaxN ((K-N) / K) Where: G = change in population size rmax = maximum net reproduction per individual N = population size K = carrying capacity 12 10 The term (K-N) / K represents the effect of carrying capacity on population growth 8 6 If N is small, the term (K-N) / K is close to one and has little effect on population 4 growth 2 0 If N is closer to K, the term (K-N) / K is close to zero and has a strong effect on 1 2 3 4 5 6 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.  Intraspecific competition The logistics model describes intraspecific competition, the dependence of two or more individuals of the same species (in the same population) on the same limiting resource. For animals, limiting resources can be food, water, nesting sites, refuges from predators, or space. For plants, sunlight, water, inorganic nutrients, and growing space can be limiting — resulting in uniform distribution. In laboratory cultures, small organisms such as flour beetles and Daphnia often show an S-shaped growth pattern. Large animals introduced into new environments can also show logistical growth. In nature, many organisms exhibit a delayed response (time delay) that can cause a population to oscillate above and below its carrying capacity. The size, density, age structure and ranges of populations can change from season to season and from year to year. Many factors that influence population dynamics are density-dependent – their influence increases or decreases with the density of the population. The logistics model includes the effects of density dependence in its assumption that per capita birth and death rates change with a population's density. 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.