Lecture 5 Flashcards
What characteristic makes megafauna particularly vulnerable to human overexploitation?
A. High reproductive rates
B. Low mortality rates and slow population growth
C. Large-scale migration patterns
D. Adaptation to diverse climates
B
Explanation: Megafauna, being K-strategists, have slow population growth and low mortality rates, making recovery from overexploitation challenging.
Which event is linked to the decline in megafauna in Australia during the late Pleistocene?
A. Massive volcanic eruptions
B. The arrival of humans
C. Abrupt climate cooling
D. Increased predation by smaller carnivores
B
Explanation: Evidence suggests that human impact, not climate change, caused the extinction of many large species in Australia.
Explain how the loss of megafauna impacts the physical structure of ecosystems.
Megafauna shape habitat structure by consuming, trampling, and breaking vegetation. Their loss often leads to denser vegetation, reduced biodiversity, and changes in plant community composition.
Explanation: Studies show ecosystems without megafauna become dominated by woody plants, altering habitat availability for other species.
Describe the role of Sporormiella fungi in understanding past megafaunal populations.
Sporormiella spores, which grow on herbivore dung, indicate the abundance of large herbivores in historical ecosystems. Their decline in sediment records signals a decrease in megafaunal populations.
Explanation: Such data correlate with shifts in vegetation and increased fire frequency, helping reconstruct ecological changes.
Analyze the relationship between megafaunal decline and global nutrient cycles.
Megafauna accelerated nutrient cycling through their consumption, digestion, and defecation, redistributing nutrients across ecosystems. Their decline slows nutrient turnover, reducing ecosystem productivity.
Explanation: Examples include reduced phosphorus transfer in oceans due to whale population declines, highlighting the megafaunal role in nutrient dynamics.
Evaluate the effects of rewilding on ecosystem trophic structures.
Rewilding can restore top-down trophic interactions, stabilize ecosystems, and increase biodiversity. However, species introductions carry risks, such as unforeseen competition or disease transmission.
Explanation: Projects like wolf reintroduction in Yellowstone show success, but require careful ecological and societal evaluation.
Case Study: Evaluate the impacts of wolf reintroduction in Yellowstone National Park on riparian ecosystems.
Wolves reduced elk populations and altered their grazing habits, enabling riparian vegetation to recover. This improved stream morphology and biodiversity, such as the return of beavers and riparian bird species.
Explanation: Wolves act as keystone species, showcasing the benefits of trophic cascades in ecosystem restoration.
Case Study: Discuss the ecological consequences of the bison kill-off in North America during the 1800s.
The massive reduction of bison disrupted grassland ecosystems, reducing nutrient recycling and altering vegetation patterns. This impacted soil health and contributed to prairie degradation.
Explanation: Bison were essential for maintaining grassland biodiversity and nutrient dynamics, demonstrating the wide-ranging effects of megafaunal loss.
What key factor contributed to the vegetation shift in Australia post-megafaunal extinction?
A. Increased browsing pressure
B. Decline in fire-adapted vegetation
C. Relaxed herbivory pressure and increased fire incidence
D. Introduction of invasive plant species
C
Explanation: The absence of herbivory led to denser, fire-adapted forests, a stark ecological shift.
Define “trophic rewilding” and give one example of its implementation.
Trophic rewilding is restoring top-down trophic interactions through species reintroduction, promoting self-regulating ecosystems. Example: Reintroduction of musk oxen in Siberia to restore steppe ecosystems.
Explanation: This approach uses keystone species to reestablish lost ecological functions.
Analyze the potential consequences of de-extinction as a conservation strategy.
While it may restore lost ecological functions, de-extinction risks include resource diversion from extant species, disease transmission, and unpredictable ecosystem impacts.
Explanation: Critics argue that it could reduce public concern for endangered species and create invasive dynamics.
What is the significance of large herbivores in maintaining vegetation community composition?
Large herbivores shape vegetation communities by consuming woody vegetation, suppressing smaller herbivores through competition, and dispersing seeds.
Explanation: Their absence can lead to denser vegetation and shifts in plant species diversity over time.
How do large carnivores contribute to ecosystem stability?
Large carnivores regulate herbivore populations and mesopredators, preventing overgrazing and maintaining biodiversity through trophic cascades.
Explanation: Their loss can disrupt food web dynamics, leading to habitat degradation and species extinction.
Describe the concept of the “megafauna fruit syndrome.”
The “megafauna fruit syndrome” refers to the evolution of fruit traits suited for consumption and dispersal by large herbivores.
Explanation: The extinction of megafauna may have impacted the distribution and genetic diversity of these plant species.
What evidence links megafaunal extinction to changes in global methane levels?
Historical events like the Pleistocene megafauna extinction reduced methane emissions, contributing to a slight global temperature decrease.
Explanation: Methane is a potent greenhouse gas, and its reduction likely impacted Earth’s climate systems.
Explain how nutrient cycling by whales affects ocean ecosystems.
Whales transport nutrients from deep ocean layers to surface waters through feces and physical mixing, supporting primary production.
Explanation: Their decline has diminished this “vertical nutrient pump,” affecting marine food webs.
What are the three key guidelines for species selection in trophic rewilding projects?
Match ecological traits to functions, consider phylogenetic relatedness, and ensure suitability for current and future ecosystems.
Explanation: These guidelines help balance ecological benefits with potential risks in rewilding efforts.
Analyze the ecological consequences of the decline in megafauna on South American savannas.
The loss of megafauna led to denser tree cover, reduced open grasslands, and altered fire regimes. This changed habitat availability and biodiversity.
Explanation: Herbivory pressure once maintained grassland ecosystems; its absence shifted the ecological balance.
Evaluate the challenges of de-extinction projects like the Pyrenean ibex cloning attempt.
Challenges include low survival rates, ethical concerns, resource allocation, and the risks of ecological mismatch or disease.
Explanation: Despite advancements in genetic technology, de-extinction faces significant technical, ecological, and societal barriers.
Discuss the interconnectivity of oceanic and terrestrial nutrient pumps involving megafauna.
Oceanic megafauna (whales) move nutrients vertically, while migratory fish and seabirds transfer them to land. Terrestrial megafauna then distribute nutrients across continents.
Explanation: This interconnected system counteracts nutrient loss to ocean sediments, demonstrating the global impact of megafauna.
