TOPIC 2: Ecology

2.1 Individuals, Populations, Communities & Ecosystems

2.2 Energy & Biomass in Ecosystems

2.3 Biogeochemical Cycles

2.4 Climate & Biomes

2.5 Zonation, Succession & ∆Ecosystems

Guiding Question

• How can natural systems be modeled, & can these models be used to predict the effects of human disturbance?

2.1 SL Knowledge & Understandings (6hrs)

1. The biosphere is an ecological system composed of individuals, populations, communities, ecosystems.
2. An individual organism is a member of a species.
3. Classification of organisms allows for efficient identification & prediction of characteristics.
4. Taxonomists use a variety of tools to identify an organism.
5. A population is a group of organisms of the same species living in the same area at the same time, & which are capable of interbreeding.
6. Factors that determine the distribution of a population can be abiotic or biotic.
7. Temperature, sunlight, pH, salinity, dissolved oxygen & soil texture are examples of many abiotic factors that affect species distributions in ecosystems.
8. A niche describes the particular set of abiotic & biotic conditions & resources upon which an organism or a population depends.
9. Populations interact in ecosystems by herbivory, predation, parasitism, mutualism, disease & competition, with ecological, behavioral & evolutionary consequences.
10. Carrying capacity is the maximum size of a population determined by competition for limited resources.
11. Population size is regulated by density-dependent factors & negative feedback mechanisms.
12. Population growth can either be exponential or limited by carrying capacity.
13. Limiting factors on the growth of human populations have increasingly been eliminated, resulting in consequences for sustainability of ecosystems.
14. Carrying capacity cannot be easily assessed for human populations.
15. Population abundance can be estimated using random sampling, systematic sampling or transect sampling.
16. Random quadrat sampling can be used to estimate population size for non-mobile organisms.
17. Capture–mark–release–recapture & the Lincoln index can be used to estimate population size for mobile organisms.
18. A community is a collection of interacting populations within the ecosystem.
19. Habitat is the location in which a community, species, population or organism lives.
20. Ecosystems are open systems in which both energy & matter can enter & exit.
21. Sustainability is a natural property of ecosystems.
22. Human activity can lead to tipping points in ecosystem stability.
23. Keystone species have a role in the sustainability of ecosystems.
24. The planetary boundaries model indicates that changes to biosphere integrity have passed a critical threshold.
25. To avoid critical tipping points, loss of biosphere integrity needs to be reversed.

2.1 Additional HL Knowledge & Understandings (⁺3hrs)

• There are advantages of using a method of classification that illustrates evolutionary relationships in a clade.
• There are difficulties in classifying organisms into the traditional hierarchy of taxa.
• The niche of a species can be defined as fundamental or realized.
• Life cycles vary between species in reproductive behavior and lifespan.
• Knowledge of species’ classifications, niche requirements and life cycles help us to understand the extent of human impacts upon them.

Expected & Ancillary Vocabulary

• reductionism, holism
• organism, organ, cell, organelle (nucleus), DNA, protein, molecule, atom, nucleus, particle, bit
• species / spp.
• population (NIR)
• habitat
• abiotic
• edaphic
• substrate
• salinity
• biotic
• detritus
• predation
• herbivory
• parasitism
• mutualism
• pathogen
• selective breeding
• quadrat
• trophic
• fieldwork
• transect (line & belt)
• biosphere
• biomass

• community
• ecosystem
• respiration
• photosynthesis
• primary producer
• autotroph
• heterotroph
• producer
• consumer
• decomposer
• competition
• intraspecific & interspecific
• competitive exclusion principle
• s-curve (sigmoidal / logistic)
• j-curve (exponential)
• carrying capacity
• limiting factors
• density-dependent
• density-independent
• emigration
• niche (fundamental & realized)
• plenary boundary
• ​

↗ Clickable IGO’s, GO’s, NGO’s & Citizen Science (IA?) →

2.5.2 iNaturalist (← click for website)

• Joint project between California Academy of Sciences & National Geographic Society

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• “Citizen science” powered using Android & iOS

• Reviewed & curated by experts

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City Nature Challenge a global & citizen challenge to cities since 2015

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Biological Levels of Organization

• Descending

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• Species
• Organism/Individual
• Organ system
• Tissue
• Cell
• Organelles
• DNA

Ecological Levels of Organization

• Organism/Individual
• Species
• Population (taxonomy)
• Community
• Ecosystem
• Biome
• Biosphere

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• Ascending

2.1.1 (1.2.7) Scaling of Systems - Reductionistic & Holistic

Ecosystem

• Biotic & abiotic
• Inputs of nutrients, water, energy
• Feeding relationships
• Trophic levels
• Organisms (Im/E)migration
• Boundary (artificial or natural)
• Feedback mechanisms
• ​

Global

• Biosphere
• Atmosphere
• Hydrosphere
• Cryosphere
• Geosphere
• Pedosphere
• Lithosphere
• ​

2.1.2_5 What is a Species (spp)?

Organisms that can interbreed & produce fertile young… are any of these a species?

Climate & the Hybridized “Grolar Bear”

2.1.5 (8.1.3) Population

…a group of individuals of the same species living in the same area at the same time, e.g., sea lions

Growth rate is NIR, or percentage variation between the number of individuals in a population at two different times

Δt = t₁ - t₀

Can be positive or negative

• main factors of increase are birth & immigration
• main factors of decrease are death & emigration

2.1.3 Scientific Revolution & the Age of Enlightenment

Early 16^th→19^th centuries, characterized by

• overthrow of religion & traditional authority in favor of of free speech & thought (democracy)
• Aristotelian doctrines (natural philosophy) dropped for Copernican (natural sciences)
• Newton’s Principia, Encyclopedia Britannica, Smith’s The Wealth of Nations, Kepler’s Astronomia Nova…
• Royal Societies founded, taxonomy (classification), metrology (SI units)
• French revolution (Napoleon, Voltaire, du Châtelet, Lavoisier…)

Astronom Kopernik, czyli rozmowa z Bogiem, by Jan Matejko

2.1.3 TOK: Why do humans classify?

2.1.3 (2.1.26) Taxonomy

…the naming, conception, & classification of groups of organisms (taxon / taxa)

• Gr. τάξις 'arrangement' & -νομία 'method'
• Swedish biologist Carl (La: Carolus) Linnaeus (1707-1778) wrote Systema Naturæ (1735) among other books in setting up
• binomial nomenclature- genus & spp naming convention (always in Latin)
• Homo sapiens → H. sapiens
• Now (Whittaker 1969) called systematics in biology, studying
• morphology
• physiology
• molecular biology
• behavior
• ecology
• geology

2.1.4 Classification Tools

Dichotomous key - identification of “spp” in binary steps based on existing specimens. Steps to create one here.

Cladogram HL - branching diagram to show evolutionary relations. Steps to create one here.

2.1.6_7 (x.x.x) Abiotic Factors

• day length
• wind velocity
• soil/edaphic factors
• chemical composition
• pH
• moisture
• separate sizes
• temperature
• snow cover (subnivean)
• precipitation
• humidity
• ​
• ​

• water/aquatic factors
• pH
• salinity
• turbidity
• dissolved oxygen
• nitrates
• phosphates
• medium/substrate
• pollutant levels
• elevation/altitude
• slope gradient
• ​
• ​

Non-living, physical, or chemical components of ecosystems. Some examples are:

1. State the proper SI units for one column of the abiotic factors above. [5]
2. Identify two abiotic factors not listed above. [1]

2.1.6_7 (x.x.x) Biotic Factors

Interactions/Interdependence/Interrelationships of living things like

• intraspecific - within a spp
• nesting/homes
• mates
• interspecific - between spp
• predator-prey
• parasitism
• in situ / ex situ - within or outside of a spp’s natural environment

Byproducts of living things, such as

• waste/feces
• dead organisms
• shed body-parts (detritus)
• What is an owl pellet?

2.1.18 (x.x.x) A Community is…

…a group of populations interacting in a common habitat.

… can be named after the dominant plant form (spp), e.g., grassland community is dominated by grasses, though it may contain herbs, shrubs, & trees, along with associated animals of different species.

…not fixed or rigid; may be large or small. Based on size & degree of relative independence, communities may be divided into two types:

1. Major communities - largely independent from anything besides sun’s energy, e.g., Ukrainian Steppe Nature Reserve grassland
2. Minor communities - dependent on neighboring communities, e.g., algal bloom on the surface of village pond

2.1.18 A Habitat is…

…the natural environment a species (or population of species) normally lives, including abiotic factors.

3. This is a picture of a region in Azerbaijan.
1. Identify four habitats in the picture at right. [2]
2. State three abiotic factors in one of the habitats named above. [3]

2.1.8 (x.x.x) Niches & Spp

The set of abiotic and biotic conditions and resources necessary for an organism to survive.

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A niche comprises:

• the habitat in which the organism lives
• the organism’s activity pattern (periods of time it’s active)
• the resources it obtains from the habitat

2.1.9 (2.2.10) Feeding Relationships

• Predation
• predator-prey
• Herbivory
• primary consumer
• Symbiosis
• Parasitism
• Ectoparasites
• Endoparasites
• Mutualism
• Disease
• pathogens (bacteria, viruses, fungi, protozoa)
• Competition
• intraspecific
• interspecific
• Neutralism

Retrieved on 31-03-2014 from: http://upload.wikimedia.org/wikipedia/commons/2/2a/ConsumerWikiPDiag.jpg

Real World Vocabulary

Match each term at left with the proper example listed.

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• mistletoe (jmeli bile, Viscum album) in apple tree (Malus spp.)
• top predator
• woodland
• aphids defended by ants
• a slow worm (slepys, Anguilis fragilis) eats a slug
• song thrushes (drozd spevny, Turdus philomelos) sing to establish a territory
• deer eating grass

2.1.10 (1.3.13) Carrying Capacity (K)

the population of a species an area or given region (in ha) can support without environmental degradation.

Sigmoid growth curves slow from exponential growth before reaching an area’s carrying capacity (K)

• equilibrium type?
• limiting factors?
• EF ∝ 1/K

2.1.10 (x.x.x) Factors Affecting K

Competition within a spp (intraspecific) &/or between spp (interspecific)

Natural & human-caused catastrophes

Immigration & emigration

Seasonal fluctuations

• food
• water
• shelter
• nesting sites

2.1.10 (x.x.x) Kaibab Plateau

Real World: Grand Canyon National Game Preserve, USA (1906)

• pop. ~4 000 mule deer (Odocoileus hemionus)
• overgrazing
• locals hunting mountain lions, bobcats, coyotes, & wolves

Suggest what happens next…

• Grand Canyon National Park established in 1919…
• Forest Service came up with 3 options
• nothing
• trapping & emigrating deer
• open deer hunting season
• 1924 they did all three

2.1.10 (x.x.x) Kaibab Plateau Management

2.1.10 Continued Management

Was Aldo Leopold Right About the Kaibab Deer Herd? (JSTOR)

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Other management regions

2.1.11 (x.x.x) Factors Affecting K

Photosynthesizer abiotic factors:

• sunlight, nutrients, substrate, CO₂, water, temperature, pH…

Consumer abiotic factors:

• climate, water, space, natural disasters, O₂, O₃…

Biotic factors:

• density-dependent
• density-independent
• typically abiotic, e.g., natural disasters
• increases death / decreases birth rates
• interactions (e.g., mating)

2.1.11 (x.x.x) Density-dependent Factors

Biotic in nature

• increases with population increase
• negative feedback mechanisms
• e.g., predator-prey, mutualism…
• intraspecific - within a species
• food supply
• territory (nesting, mates…
• density-dependent fertility
• external (interspecific) - between species
• predation, parasitism…
• disease & pandemics

2.1.12 (8.1.4) Population Growth

Types of growth rates (gradient):

• Linear
• J-curve - exponential
• S-curve - logistic / sigmoidal

Calculus - the study of continuous change:

• Differential - instantaneous change, slopes of gradients & curves
• Integral - accumulation of quantities & areas under (or between) curves

Worldometer

2.1.12 (8.1.4) Population Ecology & K → IA?

Logistic Growth:

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Competitive Lotka-Volterra Equations:

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Island Biogeography:

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Species-area Relationship:

Variable definitions

• N: number of individuals (i.e., population)
• Subscripts indicate different spp in competition
• t: time (usually in years)
• r: growth rate (i.e., RNI for humans)
• K: carrying capacity

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• α: competitive effect of spp 2 on spp 1
• Also works for predation & parasitism
• Always positive

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• S: number of species (richness)
• I: immigration
• P: initial population of spp
• E: extinctions

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• c: constant dependent on one spp in one unit area
• z: gradient of the spp-area relationship in log-log space
• A: habitat area

2.1.14 (x.x.x) K Models - Malthusian

Reverend Thomas Malthus An Essay on the Principle of Population (1798):

• food is the limiting factor
• exponential population growth vs. arithmetic food growth
• refers to environmental limits
• The Club of Rome (NGO) is neo-Malthusian

Limitations of Malthusian theory:

• ignores the poor (most affected; likely distribution problems)
• agrarian technology & economies
• a football pitch (1 ha) supports 1 000 people
• no globalization – import/export

2.1.14 (x.x.x) K Models - Boserup (Qay’s “Theory”)

Ester Boserup - Danish economist (1901-1999) The Conditions of Agricultural Growth (1970)

• population (density) is the limiting factor
• exponential population growth vs. stepwise food growth
• when food pressures exist, production increases
• machinery, fertilizer, workforce
• “necessity is the mother of invention”
• favorite among technocentrists

Limitations of Boserup’s/Qay’s Theory

• like Malthus, infers closed system (no immigration/ emigration)
• globalization ignored – import/export
• overpopulation can lead to unsustainable farming

2.1.13 (x.x.x) Humans Pushing Beyond K…

…at least their local carrying capacity, by:

• exploring
• colonization
• innovation
• invention
• resource dynamics
• resource needs
• urban vs. rural
• socioeconomic status
• technology
• import/export
• pollution levels
• medicine
• ​
• ​

2.1.15 (5.2.x) Agricultural (Agro) Technologies

Technologies since Malthus:

• reclaiming land from sea
• cross-breeding cattle
• selectively breeding high-yield crops
• terracing
• greenhouses
• sophisticated irrigation
• new food dynamics (soya, palm)
• synthetic fertilizers
• farming native species
• aquaculture
• genetically modified organisms (GMOs)
• ​
• ​

2.1.15 (x.x.x) Sampling → to Make A Mathematical Model IA?

Why? Cannot measure every organism due to

• time
• money
• resource use
• destruction (ethics)

So, sample a small set, then multiply in 2D units to the proper size...

Techniques

• Random
• least biased
• can be poor representation
• uses random number generator (RAND) or tables;
• best in uniform ecosystems
• Systematic
• regular/uniform intervals
• coverage can be better than random, but may be more biased;
• best along environmental gradients
• Stratified
• systematic & random;
• uses proportions so flexible & representations are more “true”
• proportions may be hard to identify
• best in ecosystem with varying habitats

2.1.15 (2.5.2) Types of Transects

…a straight line or narrow section through an object or natural feature or across the earth's surface, along which observations are made or measurements taken.

2.1.15 (x.x.x) Repeatability & Reliability IA?

Trials & Treatments

Take enough data so you have a confidence level that no statistical analysis will reveal another conclusion with the given amount of data. Usually 5 trials for each of 5 treatments (change in IV): 5 x 5 = 25

Method

Control variables (CVs) are measurable, explicitly stated & consideration is given to predict what may result from one or more not being strictly controlled.

Correlation & Causation

Test the statistical relationship between variables, or the stricter boundary of changing one variable to observe a direct change in another.

2.1.15 (x.x.x) How Much Data IA?

Richness is simplest measure of diversity

• number of spp in a community
• does not consider the # of individuals in a spp (this is abundance)

When do you stop taking samples? →

Look at the “species discovery curve for the sampled bird community suggesting that our sampling effort was nearly complete as more than 90% of the species available in Saadani National Park were recorded during the inventory process.”

• from Composition and Functional Diversity in Bird Communities in a Protected Humid Coastal Savanna

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4. Compare and contrast random and systematic sampling, and explain how to improve the results of one of them. [7]

2.1.16 (x.x.x) Quadrats

5. Outline a method for using a quadrat. [3]
1. Place the frame over sample area
2. Draw a 10 x 10 area in your notebook with labeled rows & columns
3. Decide how many smaller quadrats (mini-squares) you will sample (should be 10-20% of the total)
4. Randomly select these squares to sample & shade these in on your notebook diagram.
5. For ONE species at a time, count how many of them are in each of your SAMPLED quadrats (#’s or % cover)
6. Use the formula to calculate the population density for that ONE species

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7. FYI, each small quadrat for this frame = 10cm x 10cm.

NOTE: 1 m² = 10 000 cm²

• Write down the population density for each species sampled per m²

NOTE: Percent cover can total more than 100% in one quadrat

2.1.16 (x.x.x) Quadrats

Used for counting non-motile organisms, population density

Units of # of individuals or % cover

Size should be specific to organisms & habitat, typically 0.01 m², 0.25 m² or 1 m².

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6. In the figure at left, estimate [5]
1. the population of the invasive plant spp Alternanthera philoxeroides in Figure A.
2. the percent frequency of A. philoxeroides in B.
3. the percent cover in all frames, A, B, C & D.
7. Suggest how these numbers may change if observations repeated in six months. [4]

2.1.15 (x.x.x) Presentation & Processing IA?

Kite graphs - used to represent distributional data for non-motile spp along an environmental gradient

• elongated figures drawn along a base equilibrium pt. (0)
• species richness determines # of baselines
• represent changes in species abundance across an area (width between curves), scaled as
• # of organisms
• % cover
• correlation between distance &
• niches, abiotic factors, human impacts…
• dispersion & distribution data

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8. Explain how statistics can be used to communicate uncertainty. [4]

2.1.17 (x.x.x) Lincoln, Petersen, Lincoln-Petersen Index, Petersen-Lincoln Method or Capture-mark-recapture

First documented use in 1896 by Danish marine biologist C.G. Johannes Petersen & further described by American ornithologist Frederick Charles Lincoln in 1930. Used for

• estimating a motile or migrating organism’s population.
• detecting long-term population trends.
• assessing life span or reproductive output.
• tracking migration.

Not all mark-recapture involves physical recapture. Many cases the “recapture” is just re-seeing the individual.

Capture with traps (pitfall, tullgren funnel, photo/light/camera…) ethically!

2.1.17 (x.x.x) Marking Ethically

Marking samples must be

• ethically acceptable
• non-conspicuous
• will not increase predation or decrease mating potential
• paint, Sharpie™, nail polish on insects
• clipped fur, collar tags on mammals
• spray painting livestock
• PIT & VIE tags on fishes
• UV fluorescing alpha numeric tags injected under skin
• scale branding in snakes
• toe clipping in lizards and amphibians
• sewing colored beads onto tails of reptiles
• birds band

Diversity of animal identification techniques: From 'fire age' to 'electronic age'

2.1.17 (x.x.x) Mathematics & the Lincoln Index

2.1.20 An Ecosystem…

…is a community & the physical environment (abiotic factors) with which it interacts.

…includes plants, trees, animals, fish, birds, micro-organisms, water, soil, people…

…vary greatly in size and number of elements - as small as a single tree or as large as entire forest.

…creates interdependence between spp and elements that are part of the community. If one part is damaged or disappears, it has an impact on everything else.

…is healthy (i.e. sustainable) when all elements live in balance and are capable of reproducing.

2.1.20 Named Ecosystems…

Yellowstone National Park, USA

Saxon Switzerland National Park

Atacama Desert, Chile

Lake Naivasha, Kenya

East Siberian Taiga, Russia

Southern Australian Reef, Australia

Papahānaumokuākea Marine National Monument, USA

Şirvan National Park, Azerbaijan

Ras Mohammed National Park, Egypt

Real World Vocabulary

Real World: Match each term on the left with an example from the list taken from Divoká Šárka, a managed city park in Prague, CZ.

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• oak tree (dub, Quercus spp.)
• feather grass → hare (zajic polni, Lepus europaeus) → buzzard (kane lesni, Buteo buteo)
• all the living organisms in Divoká Šárka
• fungus
• day length
• deer (srnec obecny, Capreolus capreolus)
• all the living things in Divoká Šárka and the physical environment with which they interact
• temperate deciduous forest
• fox (liska obecna, Vulpes vulpes)
• all the kestrels (postolka obecna, Falco tinnunculus) in the world
• the kestrels in Divoká Šárka

2.1.20 (1.2.16) Ecosystems are Open Systems

Energy, primarily from solar irradiance, is captured through photosynthesis.

Transferred through trophic levels inefficiently (Lindeman’s 10% Law), resulting in heat loss (cellular respiration)

Matter transforms through nutrient cycling of elements & molecules like carbon, nitrogen, and phosphorus within the ecosystem.

Decomposers & detritivores recycle nutrients from dead organisms back into the environment.

BIG IDEA FOR HEALTHY ECOSYSTEMS

Matter cycles within

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Energy flows through

2.1.20 (2.3.6) Ecosystems Are Open

9. Define and give a named example of the following: [3]
1. Open system
2. Closed system
3. Isolated system

2.1.20 (2.2.11) Energy Stores & Pathways (Sankey Diagram)

…width of arrows is to scale, such as this solar irradiance figure at right.

2.1.21 (2.5.8) Ecosystem Stability

Inputs & outputs find steady-state equilibrium:

• Sunlight (UV, visible, IR) is the primary energy source for ecosystems, thermal energy released from organisms through cellular respiration.
• Nutrients absorbed from soil, water and air sustain organisms, while decomposers break down organic material back into nutrients.
• Other inputs, like water, enter (precipitation) & leave (evapotranspiration) through balanced rates.

Processes/Transformations within ecosystems:

• Photosynthesis,
• Nutrient cycling,
• Cellular respiration,
• Converting energy into other storages
• 1^st & 2^nd Laws of Thermodynamics

2.1.21 (3.1.2) Ecosystem Stability

Three factors determine stability

• Inertia – resistance to being altered (complex food webs/long-lived or dormant species)
• Resilience – ability to recover after a disturbance (nutrient-rich soils)
• Diversity – number and proportions of species present (Simpson’s Diversity Index or its reciprocal)

More diversity = more niches = more spp = more complex food webs = more resilience

• Tropical rainforest – high diversity & inertia, but low resilience (takes a long time to recover)
• Grasslands – low diversity & inertia (burns easily), but high resilience

2.1.22 (8.2.7) Humans…

…affect ecosystem resilience through reducing stores.

2.1.22 (3.2.x) Humans…

…affect ecosystem resilience through reducing diversity.

2.1.23 (x.x.x) Keystone (Umbrella) Species

• regulate populations
• support processes
• enhance biodiversity
• bolster resilience

If These 8 Spp Go Extinct, Entire Ecosystems Will Disappear (bees, sea otters, tiger sharks, prairie dogs…)

If keystone spp removed, may lead to

• trophic cascade
• biodiversity loss
• habitat degradation

2.1.24 (1.3.19) Boundaries on the Biosphere

2.1.24 (x.x.x) After BII

Estimated Biodiversity Intactness Index (BII) in the year 2020 at 0.25 degree resolution. Only the darkest areas have retained enough natural biodiversity to be within the proposed planetary boundary (where BII is above 90%).

2.1.25 (x.x.x) Critical Tipping Points - Hotspots

regions that contain a high level of species diversity, many endemic species (species not found anywhere else in the world) and a significant number of threatened or endangered spp.

Real World: research one of the regions at right and create a 3 minute public service announcement (PSA).

2.1 Additional HL Knowledge & Understandings

• There are advantages of using a method of classification that illustrates evolutionary relationships in a clade.
• There are difficulties in classifying organisms into the traditional hierarchy of taxa.
• The niche of a species can be defined as fundamental or realized.
• Life cycles vary between species in reproductive behavior and lifespan.
• Knowledge of species’ classifications, niche requirements and life cycles help us to understand the extent of human impacts upon them.

2.1.26 (3.1.5) Evolutionary Vocabulary

Taxon (plur. - taxa) - a group of one or more populations of an organism or organisms forming a “unit” (e.g., spp, genus, family, etc. in Linnaean rank)

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Phylogeny (Gr: φῦλον "tribe" γένεσις "origin") - a pictographic hypothesis of the evolutionary relationships of a group of organisms through analysis of biological processes in a rank. Also called a phylogenetic tree.

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2.1.26 (3.1.5) Trees & Corals of Life

Clade - a group of organisms evolved from a common ancestor (aka monophyletic group)

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Cladistics - modern classification of organism groups through ancestral & derived (shared) characteristics.

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Cladogram - visual representation of a clade

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2.1.26 (x.x.x) Why Use a Clade?

Because clades are based on common ancestry, they

• reflect true ancestry - links through common, monophyletic ancestor only
• standardize communication - biologists use agreed upon classification protocols
• unravels evolutionary biodiversity - nested clades can identify diversification & adaptations when spp sidetrack from norms
• show homologous structures

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@ left: If more than one cut is needed to separate a group, it does not form a clade.

2.1.27 (x.x.x) Taxonomic Difficulties

• Morphology - homologous & analogous structures may look similar
• Amino acid sequences are more accurate for clades
• Old cladograms are being revised through reclassification:
• Groups are being divided
• Groups are being merged
• Some spp being transferred between groups

2.1.28 (x.x.x) Fundamental & Realized Niches

Fundamental - The entire niche range a species can theoretically occupy.

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Realized - The actual niche a species occupies because of competition.

2.1.28 (x.x.x) Competition & Niches

Realized - The actual niche an organism occupies because of competition (overlapping area →)

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1934 - Гео́ргий Фра́нцевич (Georgy Gause) The Struggle of Existence: competitive exclusion principle (CEP)

• “survival of the fittest”
• no two species can occupy the same niche
• can also be intraspecific

2.1.28 (x.x.x) Joseph Connell’s Barnacles

1961 Ph.D. dissertation

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Fieldwork done in Scotland on two species of barnacle (and predation by snails)

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1975 - fieldwork in San Juan Islands (WA, USA)

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Breakthrough fieldwork in biotic/abiotic interactions, meticulous observations, and competition.

2.1.29 (2.5.3) r-strategists

r-strategists:

• insects, weeds, rodents, some fish, amphibians, crustaceans, fungi
• pioneer species (colonizers)
• highly adaptable
• early reproduction
• short life
• small size
• many offspring
• no parental care
• usually prey & lower on food chains

2.1.29 K-strategists

K-strategists:

• large mammals as well as many birds, trees like oak and maple, & long-lived animals such as tortoises & alligators
• dominating species
• generalists
• slow sexual maturation
• longer living
• larger size
• few offspring, maternal
• adapted to a stable environment

2.1.29 (x.x.x) Survivorship Curves

11. Suggest and explain two distinct selective (biotic or abiotic) pressures that could result in a population exhibiting a Type II survivorship curve. [4]
12. Explain how these differences are linked to contrasting reproductive strategies and levels of parental investment. [4]
13. Identify the scaling of the y-axis, and state one organism example for each curve. [3]

2.1.30 (1.2.14) Human Impacts on Spp

Life cycles of plants & animals, bacteria & fungi, seasons & climate are all an intermingled & intertwined network that is

• density-dependent,
• density independent,
• possibly quite synchronized
• fireflies
• schools of fish
• birds flying
• brain & heart cells
• happens spontaneously in nature
• shows emergent behavior through coupled oscillators (University of Sydney, 2023) & Veritasium →
• poorly understood unless studied thoroughly & often…

2.1.30 Human Impacts on Life Cycles

Watch this 3 min video about a North American genus of periodical cicadas, Magicicada.

14. Outline three ways humans may impact the cicada’s environment in terms of: [6]
1. habitat and land use.
2. climate change.
3. direct human impact.
15. Evaluate whether the cicadas' reproductive strategy is becoming more or less successful in one of the changes mentioned above. [4]