[BIO 1B] Midterm 2 Learning Objectives

Explain the nested relationships among populations, species, communities, and ecosystems.

• Populations are groups of individuals of the same species in a certain area

• Species are groups of similar organisms that can interbreed

• Communities are all the populations of different species in an area

• Ecosystems include all the living organisms in an area, as well as the non-living (abiotic) components of the environment

Interpret life history tables and survival curves, and compare and contrast key features of life histories

• Life history tables summarize demographic data for a population with features like average lifespan, age at first reproduction, number and timing of reproductive episodes, size and number of offspring, duration and investment of parental care, and survivorship

• Survival curves show the fraction of individuals surviving to different ages (Type I, II, III)

Interpret examples of life history trade-offs resulting from variation in allocation of acquisition of resources, and explain how these lead to diversity in life history strategies in variable environments

• The principle of allocation states that organisms have a limited amount of resources to invest in different functions, leading to trade-offs where investing in one function (e.g., reproduction) reduces resources available for another (e.g., survival)

• Examples include size-number trade-offs in offspring and the costs of reproduction on future reproduction

• These trade-offs result in diverse life history strategies (e.g., 'fast' vs. 'slow' species) adapted to different environmental conditions.

Given information presented as graphs, tables, or equations, describe how the size of a population has changed over time, as a result of births, immigration, deaths, and emigration

• Population size at a future time (Nt+∆t) is determined by the current population size (Nt) plus the number of births (B) and immigrants (I), minus the number of deaths (D) and emigrants (E): Nt+∆t = Nt + B + I – D – E

• Changes in these factors lead to population growth or decline.

Explain the principles of exponential and logistic growth, and how population density regulates the transition between growth phases

• Exponential growth occurs when a population has unlimited resources, resulting in a J-shaped growth curve. The rate of growth is proportional to the current population size (dN/dt = rN)

• Logistic growth occurs when resources become limited, and population growth slows as it approaches the carrying capacity (K), resulting in an S-shaped growth curve

• Density dependence (factors related to population density) regulates this transition

Apply population growth models to human societies and demographic transitions

• Population growth models, such as exponential and logistic models, can be used to understand and predict changes in human population size

• Demographic transitions involve shifts in birth and death rates as societies develop, which can influence population growth patterns

Classify species interactions by their impact on each interacting species

• Species interactions can be classified based on whether they have a positive (+), negative (-), or neutral (0) effect on each species involved

• Common types include competition (-/-), predation (+/-), herbivory (+/-), parasitism (+/-), mutualism (+/+), commensalism (+/0), and facilitation (+/+ or +/0)

Predict coevolutionary changes in species traits resulting from species interactions

• Coevolution is the reciprocal evolutionary change between interacting species

• Interactions like predation, herbivory, and competition can drive the evolution of defenses, counter-defenses, and other adaptations in the interacting species

Explain how species interactions impact the distribution and abundance of a given species, and which species are found in the same community

• Species interactions, such as competition, predation, herbivory, and mutualism, can limit where a species can live (distribution) and how many individuals can survive (abundance)

• Only species that can coexist given these interactions will be found in the same community

Contrast primary and secondary succession, describe how ecological and evolutionary processes change during stages of succession, and predict the impact of disturbance on communities

• Primary succession occurs on newly exposed or formed land with no soil (e.g., after volcanic eruption)

• Secondary succession occurs after a disturbance removes an existing community but leaves the soil intact (e.g., after a fire or storm)

• Ecological processes like species colonization, competition, and facilitation drive changes in species composition during succession

• Evolutionary processes may also play a role

• Disturbances are events that change communities and can reset the successional clock

Define a species’ fundamental and realized niche, and make inferences from data about how the niche of an organism has diverged due to coevolution (e.g. character displacement, competitive exclusion)

• A species' fundamental niche is the full range of environmental conditions and resources it could potentially use in the absence of other species

• Its realized niche is the actual set of conditions and resources it uses in the presence of other species, often limited by competition or predation

• Character displacement is the evolutionary divergence of traits in sympatric populations due to competition

• Competitive exclusion occurs when two species with identical niches cannot coexist, and one eventually eliminates the other

Explain how biologists measure biodiversity, how species richness differs from species diversity, and why plant diversity is often used as an indicator of overall biodiversity

• Biologists measure biodiversity using metrics like abundance (number of individuals), richness (number of species), evenness (relative abundance of species), and composition (identities of species)

• Species richness is simply the count of species, while species diversity often incorporates both richness and evenness

• Plant diversity is often used as an indicator because plants form the base of many food webs and provide habitat for other organisms

Analyze biodiversity data at a site and changes in biodiversity over time

• Analyzing biodiversity data involves examining metrics like richness, evenness, and abundance to understand the diversity of a community

• Changes in these metrics over time can indicate responses to environmental change, disturbance, or conservation efforts

Describe global patterns of biodiversity and the processes leading to these patterns, and how they have shifted through time

• A major global pattern is the latitudinal diversity gradient (LDG), with higher species richness near the equator

• Explanations include more land area, less stressful environments, more energy, higher speciation rates, and longer evolutionary time in the tropics

• These patterns have shifted throughout Earth's history due to continental drift and climate change

Analyze the consequences of changing a community's distribution from the continuous occupation of a broad area to occupying small, disconnected patches within the same area

• Fragmenting a continuous habitat into small, isolated patches (habitat fragmentation) can lead to lower biodiversity due to increased extinction rates (smaller populations, edge effects), reduced immigration rates (isolation), and the disruption of ecological processes

• The species-area relationship and island biogeography theory help explain these consequences

Explain the difference between abiotic and biotic factors, and provide examples of how these factors can affect the species present

• Abiotic factors are the non-living components of the environment (e.g., temperature, precipitation, light, nutrients)

• Biotic factors are the living components (e.g., other organisms, competition, predation, disease)

• Both types of factors influence the survival, growth, and reproduction of species and therefore affect which species can live in a particular are

Explain how abiotic variables such as temperature, precipitation, light, or other factors change along environmental gradients such as elevation, latitude, and depth, and describe the processes leading to those gradients

• Abiotic variables change predictably along environmental gradients

• For example, temperature generally decreases with increasing elevation and latitude due to changes in atmospheric pressure and solar radiation

• Precipitation can vary with latitude due to global air circulation patterns like Hadley cells and with elevation due to orographic effects (rain shadow)

• Light intensity decreases with depth in aquatic environments

Predict the consequences of changes in primary production due to perturbations such as drought, fire, flood, extreme temperatures, or nutrient influx or loss

• Changes in primary production (the rate at which producers convert energy into biomass) can have cascading effects throughout an ecosystem

• Decreases (e.g., from drought or nutrient loss) can lead to reduced energy availability for higher trophic levels

• Increases (e.g., from nutrient influx) can sometimes lead to imbalances or other negative consequences

Explain why there is typically less biomass and fewer individuals and species at the top of a food chain than at the bottom

• This is due to the inefficiency of energy transfer between trophic levels

• On average, only about 10% of the energy at one trophic level is converted into biomass at the next level (ecological efficiency)

• This limits the amount of biomass and the number of individuals and species that can be supported at higher trophic levels, resulting in trophic pyramids

Given a food web or other information on relationships among species in that community, predict the consequences of removing an apex ("top") predator, introducing a specific disease, or other specified changes occurring

• Changes at one trophic level can have trophic cascade effects on other levels

• Removing a top predator can lead to an increase in its prey, which in turn can decrease the abundance of their food source (top-down control)

• Introducing a disease can drastically reduce the population of a susceptible species, with potential consequences for its predators and prey

Explain how human activities have affected global nutrient cycles

• Human activities, such as burning fossil fuels, deforestation, agriculture (including fertilizer use and animal farming), and industrial processes, have significantly altered the global cycles of water, carbon, nitrogen, and phosphorus, often leading to imbalances and environmental problems

Describe the major events in the global cycling of water, carbon, nitrogen, and phosphorus

• The water cycle involves evaporation, transpiration, condensation, and precipitation

• The carbon cycle includes photosynthesis, respiration, decomposition, and the exchange of carbon dioxide between the atmosphere, oceans, and living organisms

• The nitrogen cycle involves nitrogen fixation, nitrification, assimilation, ammonification, and denitrification

• The phosphorus cycle involves weathering of rocks, uptake by plants, consumption by animals, and decomposition

Interpret changes in atmospheric CO2 over the past hundred thousand years

• Over the past hundred thousand years, atmospheric CO2 concentrations have fluctuated in cycles, closely correlated with glacial and interglacial periods (Ice Ages)

• These natural variations were generally between ~180 ppm (glacial periods) and ~280 ppm (interglacial periods)

• Since the Industrial Revolution, human activities have caused a rapid and substantial increase in CO2 concentrations, exceeding 400 ppm

Explain how human activities impact climate change by disrupting the global carbon cycle, and the role of positive and negative feedback mechanisms

• Human activities, primarily burning fossil fuels and land use change (deforestation), release large amounts of CO2 into the atmosphere, disrupting the natural carbon cycle and enhancing the greenhouse effect, leading to climate warming

• Positive feedback mechanisms amplify the initial warming (e.g., melting ice reducing Earth's reflectivity), while negative feedback mechanisms tend to counteract the warming (e.g., increased plant growth at higher CO2 levels)

Explain how climate warming leads to changes in the timing of seasonal events (phenology) and how changes in the phenology of one species can affect the ecology of other species

• Climate warming is causing shifts in the timing of biological events (phenology), such as earlier spring blooms, earlier migration of birds, and changes in insect emergence

• These phenological shifts in one species can lead to mismatches with the phenology of interacting species (e.g., pollinators and flowers), potentially disrupting ecological relationships and food webs

Understand how anthropogenic climate change is impacting humans and other organisms, and how these impacts differ across the globe

• Anthropogenic climate change is causing a wide range of impacts, including rising global temperatures, changes in precipitation patterns, sea-level rise, more frequent and intense extreme weather events, and shifts in species distributions

• These impacts are not uniform across the globe, with some regions and populations being more vulnerable than others due to factors like geographic location, socioeconomic status, and reliance on climate-sensitive resources

Identify ecological processes and types of pathogens and parasites that affect disease spread, and predict how global change might impact infectious disease dynamics.

• Ecological processes like host population density, dispersal, and species interactions influence disease spread

• Pathogens (disease-causing organisms) and parasites (organisms that live on or in a host, harming it) can be transmitted through contact, vehicle, or vector routes

• Global change (climate change, land use change) can alter host and pathogen distributions, transmission rates, and the emergence of new diseases

Apply population growth models to disease dynamics

• Population growth models, such as the SIR model (Susceptible-Infectious-Recovered), can be used to understand and predict the spread of infectious diseases within a population

• Key parameters include the transmission rate (β) and the recovery rate (m), which determine the basic reproductive number (R0), indicating whether an epidemic will occur.

Reflect on the history and societal implications of the field of ecology

• Ecological ideas have historical linkages to 19th-century economic concepts like 'natural resources' and 'competition', and political ideas like 'colonization' and 'invasive species'

• Western ecological science is not the only form of ecological knowledge; Indigenous Knowledge systems also hold vast understanding of environmental interactions

Reflect on the relationship of western ecological science to other knowledge systems

• Western ecological science, with its emphasis on quantitative data and experimentation, is one way of understanding ecological relationships

• Indigenous Knowledge systems, developed through long-term observation and experience, offer complementary perspectives and insights into ecological processes and sustainable resource management

Apply ecological concepts to human-dominated environments such as cities

• Urban areas are also ecosystems that influence energy and nutrient fluxes, biodiversity, and species interactions

• Ecological principles can be applied to understand and manage biodiversity, nutrient cycling, and other ecological processes in urban environments.

Describe how humans and nature are shaped by fire

• Fire is a natural disturbance in many ecosystems, and both humans and nature have adapted to it

• Many plant species have fire adaptations like thick bark, resprouting ability, and serotiny

• Indigenous peoples have traditionally used fire to manage landscapes

• Modern fire suppression can have ecological consequences in fire-adapted ecosystems

Identify key drivers and mechanisms for conserving biodiversity, the main barriers to doing so, and how to overcome them

• Key drivers for conservation include recognizing the intrinsic and instrumental value of nature

• Mechanisms include protected areas, dispersal corridors, assisted migration, and habitat restoration

• Barriers include habitat loss, climate change, overexploitation, invasive species, and pollution

• Overcoming them requires addressing the root causes, implementing effective conservation strategies, and considering ethical implications

Consider the ethical implications of conservation decisions

• Conservation decisions often involve trade-offs and ethical considerations regarding the value of nature (instrumental vs. intrinsic), the rights of nature, and the distribution of costs and benefits of conservation actions

• Different decision-making frameworks, such as economics and rights-based approaches, have different ethical implications