2.1 Individuals, Populations, Communities & Ecosystems (DP IB Environmental Systems & Societies (ESS): HL): Flashcards

An ecosystem is a community of living organisms, along with their physical environment, interacting as a system within a specific area.

Biotic components are the living parts of an ecosystem, such as plants and animals, while abiotic components are the non-living parts, such as soil, water, air, sunlight and minerals.

Ecosystems are open systems in which both energy and matter can enter and exit.

Classification is the process of organising and grouping species based on their similarities and differences.

The first step in classifying a new species is placing it into a genus, a group of closely related species.

Every species receives a two-part name: the genus followed by the species.

A genus is a classification category that includes one or more closely related species.

False.

The genus name is always written first, followed by the species name.

The genus Canis includes species such as the grey wolf, domestic dog, and coyote.

A taxonomic tool is any method or device used by taxonomists to identify and classify organisms.

Identification means determining which species an individual organism belongs to.

Reference collections are used to compare unknown specimens with identified and classified samples to help identify organisms.

DNA surveys identify species by comparing an organism's DNA sequence to known sequences in databases.

Apps can identify unknown species by comparing a photo to thousands of photos in an online database.

A dichotomous key is a tool that helps identify organisms by a series of paired statements or questions based on their characteristics.

False.

Dichotomous keys rely on physical characteristics and do not usually take behaviour into account.

One limitation of dichotomous keys is that they are usually limited to a small number of species.

Two limitations of dichotomous keys are: limited scope (they only cover certain species), and reliance on physical characteristics, which may vary.

A limiting factor is any environmental factor that restricts the size or growth of a population, such as predation, disease, or resource availability.

The removal of natural predators has allowed human populations to grow unchecked and has caused ecosystem imbalances, such as overgrazing by other species, leading to habitat degradation.

Technological advances in agriculture and medicine have reduced mortality rates and increased food production, leading to population growth.

The carrying capacity is the maximum population size that an environment can sustain indefinitely without being degraded.

Humans have a broad and dynamic ecological niche, can move and exploit resources globally, and their population dynamics are influenced by technological, cultural, and social factors, making carrying capacity estimates difficult.

Clearing forests for agriculture and urbanisation provides more living space and land for food production, boosting human population growth rates.

False.

Humans can move and exploit resources from distant locations, such as through global trade.

An ecological niche is the role and position a species has in its environment, including how it obtains resources, survives, and interacts with other organisms.

Estimates are disputed due to uncertainties in technology, changing consumption patterns, and environmental degradation.

Environmental degradation leads to habitat destruction, pollution, and resource depletion, compromising ecosystem sustainability.

An ecological niche is the particular set of abiotic and biotic conditions and resources to which an organism or population responds and depends.

Only one species can occupy a given niche because if two species attempt to do so, they will compete for the same resources, and one will out-compete the other.

A niche describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds and upon which it depends.

Three North American warbler species avoid competition by feeding at different heights within the same conifer trees, occupying slightly different niches.

If two species try to occupy the same niche, they will compete with each other for the same resources.

A population is a group of organisms of the same species living in the same area at the same time.

Populations interact in ecosystems through herbivory, predation, parasitism, mutualism, disease and competition.

When one animal eats another, this is called predation.

A mutualistic relationship is one in which both species benefit from the interaction.

Parasitism is a relationship in which the parasite benefits by obtaining resources from the host species, often harming the host.

In a stable community, the numbers of predators and prey rise and fall in cycles, limiting the carrying capacity of both populations.

Intraspecific competition is between members of the same species, while interspecific competition is between different species.

The carrying capacity of herbivore species is affected by the number of plants they feed on.

Biotic factors are the living components of an ecosystem, while abiotic factors are the non-living, physical factors such as temperature and sunlight.

Abiotic factors include temperature, sunlight, and pH, which can affect the survival and reproduction of organisms.

Carrying capacity is the maximum population size that an environment can support given its resources and conditions.

The carrying capacity is the maximum stable population size of a species that an ecosystem can support, determined by competition for limited resources.

A J-curve describes the population growth pattern in an environment with unlimited resources, showing exponential growth followed by a possible crash.

An S-population curve describes population growth in a resource-limited environment, with phases of lag, exponential growth, transitional slowing, and plateau at the carrying capacity.

A density-dependent factor is a factor whose impact on population size varies with population density, such as competition, predation, or disease.

The three phases of a J-curve are the lag phase, the exponential growth phase, and the crash phase.

The crash phase occurs when the population overshoots the carrying capacity and a limiting factor, such as disease or predation, causes a rapid decrease in population size.

False.

A J-curve population may crash if a limiting factor is encountered after exponential growth.

A J-curve describes population growth when resources are unlimited.

When density-dependent limiting factors are present, population growth follows an S-shaped (sigmoid) curve.

The four phases of an S-population curve are: lag phase, exponential growth phase, transitional phase, and plateau phase.

During the plateau phase of an S-population curve, the population fluctuates around its carrying capacity, controlled by negative feedback mechanisms.

As population density increases, competition for resources becomes more intense, limiting individual growth and reducing overall population size.

True.

Factors such as predation and disease become more significant as population density increases.

A negative feedback mechanism is a process where increasing population density triggers factors (like resource scarcity, predation, or disease) that act to return the population to its equilibrium state.

As population density rises, competition between individuals increases and can limit population size.

When a population reaches its carrying capacity, environmental factors prevent further growth, so population size fluctuates around a stable value.

The carrying capacity of a species is the maximum stable population size that an ecosystem can support.

A population is the whole set of items or organisms that you are interested in studying.

A random sample is a subset of the population where every member has an equal chance of being selected.

A population is the whole group you are interested in, while a sample is a subset of that population from which data is actually collected.

A transect is a line across a habitat along which samples are taken at regular intervals.

A quadrat is a square frame used to sample and estimate the population size or coverage of non-motile organisms, such as plants.

Quadrats are usually used to study non-motile organisms such as plants.

Percentage cover is an estimate of the area within a quadrat that is covered by a particular species.

Sampling bias can be avoided by randomly placing quadrats in the sampling area, often using random number generators to select the locations.

To estimate percentage frequency, divide the number of quadrat squares with the species present by the total number of squares, then multiply by 100.

Capture-mark-release-recapture is a method for estimating population size of motile animals by capturing, marking, releasing, and later recapturing individuals.

The Lincoln index estimates the population size or abundance of a species in a given area.

The formula for the Lincoln index is: Population size estimate = ( M × N ) ÷ R.

True.

The marking must not affect survival, visibility to predators, or behaviour, to ensure an accurate population estimate.

The assumptions are: 1) marked individuals are fully mixed back into the population, 2) the marking does not affect survival or behaviour, and 3) the population size remains constant during the study.

In the Lincoln index, M is the number of marked individuals released, N is the total number caught in the second sample, and R is the number of marked individuals recaptured.

Ecosystem sustainability is the ability of an ecosystem to maintain balance and productivity over time, supporting life and functioning effectively.

Balanced inputs and outputs mean that the energy, nutrients, and water entering an ecosystem are equal to those leaving, ensuring the ecosystem's stability and resilience.

In steady-state ecosystems, inputs and outputs are balanced to maintain long-term stability.

Ecosystem flow diagrams show the movement of energy and nutrients within ecosystems, highlighting the interconnectedness of biotic and abiotic factors.

Tropical rainforests are an example of ecosystems that have persisted for millions of years, showing long-term resilience.

Deforestation reduces transpiration, leading to less water vapour and therefore less cloud formation and precipitation, which disrupts local and regional climate systems.

A positive feedback loop caused by deforestation can make forests more vulnerable to drought and wildfires.

A tipping point is a critical threshold where small changes can trigger significant shifts in an ecosystem, possibly leading to a new equilibrium.

A keystone species is an organism that has a disproportionately large impact on an ecosystem's structure and function relative to its abundance.

Without purple sea stars, mussel populations would expand rapidly, reducing diversity on rocky shores.

African elephants help maintain habitat diversity by feeding on shrubs and trees, creating gaps in vegetation and promoting the growth of grasses, which supports a greater variety of species.

Biosphere integrity is the overall health and diversity of life on Earth, which is essential for stable ecosystems.

False.

Loss of biodiversity makes ecosystems more vulnerable to collapse by reducing their resilience and stability.

Extinction rates today are at unprecedented levels due to human activities such as habitat destruction and climate change.

Three key strategies are habitat conservation, species conservation, and sustainable resource management.

A taxonomic hierarchy is a system in which organisms are grouped into increasingly smaller and more specific taxa, with no overlap between groups.

The taxonomic hierarchy, in descending order of size, is: domain, kingdom, phylum, class, order, family, genus, species.

A taxon is a group of organisms classified together within the taxonomic hierarchy.

A hierarchical classification system is one in which larger groups contain smaller groups with no overlap between groups.

False.

Dolphins and sharks have similar body shapes due to convergent evolution, but dolphins are mammals and sharks are fish. They belong to different classes.

Morphology is the study of the observable characteristics and structure of organisms.

Morphology can be misleading because similar physical features may evolve independently in unrelated organisms, so similarities do not always indicate a recent common ancestor.

The use of genome sequencing data helps avoid difficulties with misleading morphology in classification.

Introgression is when the fertile offspring of a cross between two species go on to breed only with members of one parent species, causing genes from one species to enter the gene pool of another.

A clade is a group of organisms that includes all the descendants of a common ancestor.

A monophyletic group contains all the descendants of a single common ancestor, with no exclusions.

Cladograms show evolutionary relationships and the order of divergence using nodes to represent common ancestors.

False.

Cladistics is concerned with identifying evolutionary relationships between organisms, not naming them.

A cladogram is a diagram that shows the evolutionary relationships between species based on the order of divergence from common ancestors.

The root of a cladogram represents the common ancestor of all the organisms within it.

DNA sequencing allows organisms to be classified based on evolutionary relationships, leading to more accurate groupings and reclassification of species into appropriate clades.

A fundamental niche is the full range of conditions and resources in which a species could survive and reproduce if there were no limiting factors.

A realised niche is the actual conditions and resources in which a species exists due to biotic interactions such as competition.

A fundamental niche shows where a species could exist without limiting factors, while the realised niche shows where it actually exists due to competition and other biotic interactions.

True.

Biotic interactions like competition can restrict a species to a smaller realised niche than its fundamental niche.

The barnacle species Chthamalus dalli's realised niche is restricted to areas higher up on the shore due to competition.

The realised niche of Chthamalus dalli is smaller than its fundamental niche due to competition with Balanus glandula for space and resources.

A species' fundamental niche includes all the conditions and resources it could use, but its realised niche is limited by biotic interactions.

You can compare the fundamental niche (where a species could live without limiting factors) and the realised niche (where it actually lives due to competition and adaptations) for any species, not just those mentioned in the syllabus.

A life cycle is the series of stages an organism goes through from birth, through growth and reproduction, to death.

An r-strategist is a species that produces many offspring with little or no parental care, typically living in unstable environments.

A K-strategist is a species that produces few offspring but invests heavily in their care, usually thriving in stable environments.

The main difference is that r-strategists produce many offspring with little care, while K-strategists produce few offspring with high parental care.

Species that produce many offspring but provide little or no parental care are called r-strategists. They usually live in unstable environments.

K-strategists have few offspring and high parental care.

Understanding a species' niche and life cycle helps identify how human activities might disrupt their survival and reproduction.

Habitat destruction is when human activities such as deforestation or urban expansion remove or degrade the natural environments species need for their life cycles.

Pollution can damage the health of organisms or their habitats, which can disrupt their life cycles, reproduction, and survival.

The use of neonicotinoid pesticides in agriculture can reduce populations of insects like bees, affecting their ability to forage and reproduce.

True.

Climate change can alter temperatures and seasons, causing events like flowering or migration to occur earlier or later, leading to mismatches between species.

Melting sea ice shortens the hunting season for polar bears, reducing their fat reserves needed for reproduction and survival, and disrupting their life cycles.

Sea turtles are threatened when their nesting beaches are disturbed by tourism or development, reducing their reproductive success.

Warmer springs may cause plants to flower earlier, but if pollinators like bees do not emerge at the same time, pollination can be disrupted.

r-strategists reproduce quickly and colonise new habitats rapidly, giving them an advantage when environments are unstable or changing.