IB Environmental systems and societies 2.1O Knowledge of Species' Classification Notes

Reading a Species Through Three Lenses to Predict Human Impact

1. Knowing a species' classification, niche, and life cycle lets us predict and assess how human pressures affect it.
   1. Classification places the species in a food web and shows which relationships collapse if it declines.
   2. Niche shows the exact resources and conditions it needs, so we can see which human pressure removes them.
   3. Life cycle shows the timing and stages of reproduction, so we can spot where disruption breaks the chain.

The three strands below apply these lenses to climate change, habitat loss, and pollution.

Climate Change: When Warming Breaks the Timing of Life Cycles

1. Burning fossil fuels, deforestation, and industrial emissions are warming the climate and shifting seasons.
2. This alters the temperature, rainfall, and daylight cues that trigger breeding and migration.

Phenological Shifts

1. Warmer temperatures and changed day length push species to flower, breed, or migrate earlier than before.
2. Species tuned to seasonal cues now face mismatched signals that harm feeding and reproduction.

Trophic Mismatches

1. Warming can desynchronise interdependent species across trophic levels.
2. When prey peak before predators breed, food runs short at the most critical time.

Polar Ecosystems

1. Melting sea ice shifts the seasonal cycles of polar species.
2. Polar bears hunt seals from the sea ice.
   1. Shorter ice seasons cut feeding time, lowering fat reserves and reducing cub survival.

Habitat Destruction: When the Niche Is Physically Removed

Urbanisation, deforestation, and land conversion break the habitats species depend on across their life cycles.

Breeding and Migration Disrupted

1. Sea turtles return to specific beaches to lay eggs, but coastal development and artificial light destroy nests and disorient hatchlings.
2. Migratory birds lose stopover sites to urban sprawl, making long journeys impossible.
3. Amphibians such as frogs need wetlands to breed, so wetland loss reduces larval survival and shrinks populations.

Resource Availability Reduced

1. Fragmentation isolates populations, making mates and food harder to find.
2. Fragmented forest edges alter microclimates, cutting the food plants herbivores rely on.

Pollution: When Chemicals Attack the Life Cycle

1. Pollution harms the reproductive health, growth, and survival of organisms at many trophic levels.
2. The type of pollutant decides how a life cycle is disrupted.

Pesticides and Pollinators

1. Neonicotinoid pesticides cut bee populations by damaging their foraging, navigation, and reproduction.
2. This breaks the pollination cycles that wild plants and crops depend on.

Endocrine Disruptors

1. Chemicals such as phthalates, BPA, and synthetic hormones enter waterways from waste and agriculture.
2. They mimic natural hormones, disrupting sexual differentiation and reproductive cycles in fish and amphibians.
   1. Reduced fertility.
   2. Development of intersex individuals.
   3. Altered breeding behaviour.

Bioaccumulation and Biomagnification

1. Persistent pollutants like PCBs, mercury, and DDT build up in tissue and concentrate up the food chain, so top predators carry the highest load.
   1. The full mechanism belongs to Topics 2.2 and 4.4; here it matters because a species' trophic position predicts its exposure.

Bringing the Three Lenses Together

1. A species' trophic position, niche, and life-cycle timing together predict which human pressure hits it hardest.
2. Specialists with narrow niches and precise breeding cues are the most vulnerable to disruption.