2.1O Knowledge of species' classification (HL) Notes

1. Human activities increasingly influence the structure and function of ecosystems, altering the delicate balance between organisms and their environments.
2. To assess the extent of these impacts, ecologists study three key aspects of species:
   1. Classification: understanding the species’ position in the ecosystem and food web.
   2. Niche requirements: understanding how and where it lives, including its resource use and environmental conditions.
   3. Life cycle: understanding how it grows, reproduces, and interacts with environmental factors.

Climate Change and Disruption of Life Cycles

1. Human activities, particularly the burning of fossil fuels, deforestation, and industrial emissions, are causing significant climate alterations.
2. Climate change alters seasonal temperature patterns, rainfall, and photoperiod cues, which are critical triggers for reproductive and migratory behaviors.

Phenological Shifts

1. Changes in temperature and day length patterns lead to earlier flowering, fruiting, breeding, or migration.
2. Species adapted to seasonal cycles are now experiencing mismatched ecological cues, disrupting feeding and reproductive success.

Trophic Mismatches

1. Temperature changes can desynchronize interdependent species across trophic levels (producers, consumers, predators).
2. When prey species emerge earlier than predators, food shortages occur at critical breeding times.

Arctic and Polar Ecosystems

1. Melting ice from global warming alters the seasonal cycles of polar species.
2. Polar bears, for example, rely on sea ice to hunt seals.
3. Shorter ice seasons reduce feeding opportunities, leading to lower fat reserves, affecting reproductive rates and cub survival.

Habitat Destruction and Fragmentation

Habitat loss from urbanization, deforestation, and land conversion disrupts the continuity of ecosystems that many species rely on during their life cycles.

Impact on Breeding and Migration

1. Sea turtles return to specific beaches to lay eggs. Coastal development and artificial lighting disorient hatchlings and destroy nesting grounds.
2. Migratory birds lose stopover sites due to urban sprawl and deforestation, making long-distance migration impossible.
3. Amphibians, such as frogs, rely on wetlands for breeding. The loss or pollution of these habitats leads to reduced larval survival and population decline.

Impact on Resource Availability

1. Habitat fragmentation isolates populations, making it harder for individuals to find mates and food.
2. Fragmented forest edges alter microclimates, reducing the availability of food plants for herbivores.

Pollution and Contamination

1. Pollution affects the reproductive health, growth, and survival of organisms across multiple trophic levels.
2. The type of pollution determines how life cycles are disrupted.

1. Pesticides and Pollinators

1. Widespread use of neonicotinoid pesticides reduces bee populations by affecting their foraging ability, navigation, and reproduction.
2. This disrupts pollination cycles essential for both wild plants and agricultural crops.

2. Endocrine Disruptors

1. Chemicals such as phthalates, bisphenol A (BPA), and synthetic hormones enter waterways from waste and agriculture.
2. They mimic natural hormones, interfering with sexual differentiation and reproductive cycles in fish and amphibians.
3. Results include:
   1. Reduced fertility.
   2. Development of intersex individuals.
   3. Altered breeding behavior.

3. Bioaccumulation and Biomagnification

1. Persistent pollutants like PCBs, mercury, and DDT accumulate in organisms over time (bioaccumulation) and become more concentrated at higher trophic levels (biomagnification).
2. Top predators (e.g., eagles, whales, humans) exhibit the highest contamination.