exam gaps Flashcards
(35 cards)
2 classes of adaptations for surviving fire
- Post-Fire Re-Sprouting (Individual Survival)
* Dormant Buds:
○ Aerial Buds: Epicormic buds are typically suppressed under an intact canopy, but post-fire canopy loss triggers growth via hormonal changes.
○ Underground Buds: Buds in structures like lignotubers, rhizomes, and root suckers enable re-sprouting after fires. Examples: Acacia species, mallee eucalypts.
* Thick, Fibrous Bark: Protects crucial inner layers (phloem for nutrient transport, cambium for growth), enabling resprouting if these parts survive. - Seeding (Species Survival)
- Canopy Seed Bank: Seeds are stored in the canopy, protected in woody fruits, and released post-fire. Examples: Banksia, hakea, eucalypts.
- Soil Seed Bank: Seeds accumulate in the soil, with dormancy mechanisms activated by fire-cracked seed coats, aiding germination. Examples: Peas, acacias.
- Myrmecochory (Ant-Dispersal): Seeds have nutrient-rich elaiosomes (funicles), attracting ants that carry seeds underground, storing them in nests and aiding germination after discard.
How does fire stimulate germination
- Smoke: Contains butenolide (a by-product of burning cellulose) that breaks seed dormancy, and ethylene, a plant hormone, which promotes flowering in species like Xanthorrhoea and Kingia.
- Nutrient-Rich Ash Bed: The post-fire influx of nutrients in ash promotes growth, supporting larger populations with reduced competition.
- Resprouting: Xanthorrhoea also re-sprouts leaves from its trunk after fire damage, aiding in recovery.
What is conservation
Conservation is about trying to halt and reverse biodiversity loss caused by humans, including extinctions
Why is conservation important
- Utilitarian: focusing on the benefits people can get from nature
People and nature: complex combination of inherent values, managing threats, human rights, and both impacts on and benefits from nature
What are the types of extinction
Extinct: no individuals remaining
* Locally extinct: Extinct from part of its range, but still exists elsewhere
* Extinct in the wild: Still in captivity but not longer found in its natural habitat
* Functionally extinct: No longer enough individuals present to fulfil their role in the ecosystem
* Co-extinction: When the loss of one species leads to the loss of another
* Lazarus effect: When a species is thought extinct, but rediscovered
* Ecosystem collapse: Loss of defining features: species, structure, function
Describe population persistence (viability)
- environmental stochasticity: fluctuations in population size due to chance environmental conditions
- demographic stochasticity: fluctuations in population size due to chance events of births an deaths
Describe population viability
population’s ability to persist over time, which is essential in conservation.
- Population Viability Analysis (PVA), a tool used to estimate the risk of extinction and to guide conservation decisions.
- PVA assesses the likelihood of extinction over a specific timeframe and can simulate various scenarios, such as changes in population growth rates, threats, and conservation efforts.
Conservation strategies:
- Reducing threats - the impacts of diversity loss
○ In situ - improving persistence within an ecosystem or a species’ habitat - Increasing population size
○ Ex situ - like captive breeding , reintroduction
○ In situ - improving reproductive success by restoration and/or enhancing habitat - Raising awareness and funding
○ Communities or governments on board to support conservation
○ Government funding, donations, volunteering, behaviour change
What is a threatened species?
- Decline in population size
- Small distribution and ongoing threats
- Small population size and ongoing threats
What is a threatened ecosystem?
- Loss in area
- Restricted distribution (i.e. being on an island)
- Degradation of abiotic environment (i.e. melting ice)
- Degradation of biotic processes (decline in species, interactions, and processes)
Chenopodiaceae - salt bushes and succulents
- salt on leaves reflects radiation
- covered in bladder cells on leaves to excrete excess salt
- salt is taken up by the vascular system to get rid of salt that is toxic to the cells
- the salt builds up on the outside of cells, giving its silver appearance
Cactaceae
- Succulents - fleshy, filled with watery sap, drought and salt tolerant
What are xerophytes
Xerophytes - drought tolerators, 2 major types (sclerophylls and succulents)
Drought avoiders:
- spend dry time as seeds
- grows and reproduces rapidly when there’s moisture
- seeds are dormant until germination in the wet season
Musky rat
Habitat:
* Found exclusively in the rainforests of northeastern Queensland, Australia, particularly in the Wet Tropics region.
* Prefers dense, lowland rainforest environments with plenty of ground cover and leaf litter.
* It’s dependent on moist habitats and is sensitive to habitat disturbance, which limits its range.
Diet and Foraging:
* Musky rat-kangaroos are omnivorous. They primarily feed on fruits, seeds, and fungi but also consume invertebrates.
* They are important seed dispersers, particularly for large rainforest seeds.
* Unlike other kangaroos, they are active during the day (diurnal) and spend most of their time foraging on the forest floor.
Reproduction:
* Musky rat-kangaroos breed year-round and can have multiple litters each year.
* Females typically give birth to two young, which they carry in a pouch for several months.
* They are one of the few marsupials that can conceive again shortly after giving birth (embryonic diapause)
Embryonic diapause
- Embryonic diapause is a reproductive strategy where embryo development pauses temporarily.
- The embryo remains in a dormant state within the mother’s uterus.
- This delay allows the mother to time the pregnancy to favorable conditions or until older offspring are weaned.
- Common in marsupials
- Increases reproductive success by aligning births with optimal resource availability.
The southern cassowary
Habitat:
* Found primarily in the tropical rainforests of New Guinea, northeastern Australia (Queensland), and some surrounding islands.
* Their habitats are often rich in fruiting trees, which are essential to their diet and survival.
Diet and Ecological Role:
* Southern cassowaries are frugivores, feeding mainly on fallen fruit, but they also eat fungi, insects, and small animals.
* They are essential seed dispersers, consuming whole fruits and dispersing seeds throughout the forest via their droppings.
* This seed dispersal is crucial for rainforest regeneration and helps maintain plant diversity.
Reproduction:
* Females are larger and more dominant, often mating with multiple males, while each male incubates a clutch of eggs for about 50 days. (Polyandry)
Significant Adaptations:
* The casque acts as a ‘helmet’ on their heads and may serve various functions, such as amplifying calls, protecting the head, or helping move through dense vegetation.
* The cassowary’s ability to consume and disperse large seeds that other animals cannot is crucial for forest health and plant species diversity.
Seaweed vs seagrasses
Seaweed/macroalgae
From many lineages
Fundamentally different (similar morphology)
Seagrasses/marine plants
Green plants
Share same tissue specialisation as in land plants
Vascular/flowering plants, returning to the sea
Keystone species
Keystone species: a species within a community that has a role out of proportion to its abundance, or affects overall structure of a community
Epifauna
Epifauna: benthic organisms that live on the surface of the seabed, either free-moving or attached to objects at the bottom
Infauna
Infauna: benthic organisms that dig into the seabed or construct tubes/burrows
Why do we have high endemism?
· Long isolation of Australia from when Gondwana split, there was a lot of time for species to evolve
· The east and west coastlines
· Currents help bring seaweeds from warmer tempers to cooler ones - with new habitats and adaptations
Variety of temperature gradients from tropics to poles
Climate impacts on aquatic ecosystems
Climate Change Impacts:
· Warmer, more variable sea temps
· More carbon dioxide might lead to more growth in some species, losses in others
· Proliferation in some areas, losses in others
· Seaweed farming and harvesting
· Consequences:
o Increased productivity: some thriving on carbon dioxide and runoff, grow larger and creates ‘rafts’
o Shifting species distributions: some species vulnerable
o Tropicalisation of seaweeds: changes to species composition in tropical waters
Endosymbiosis in algae
ENDOSYMBIOSIS: how the algae have formed
· Cyanobacterium swallowed by heterotrophic eukaryote and starts to live within it - primary endosymbiosis - becomes one type of algae
Secondary endosymbiosis - the primary cyanobacterium is living nicely inside the heterotrophic eukaryote, then another cyanobacterium gets swallowed by the same eukaryote - forms another type of algae
