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Environmental selection pressures on species in an ecosystem - Coggle…
Environmental selection pressures on species in an ecosystem
Selection Pressures
Natural selection comes into play
Individuals have random variations
Better suited to survive
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Only individuals that survive have variations
Surviving population is different to the original
Change in environment
Resources become limited
Individuals have to compete
Abiotic selection pressures
Temperature
Light intensity
Soil type
Water availability
Gas concentration
Biotic selection pressures
Competition between species for resources
Predators
Availability of prey
Abiotic and biotic pressures affect the abundance and distribution of an organism in an ecosystem
Abiotic factors
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a non-living part of an ecosystem that shapes its environment
Biotic factors
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a living organism that shapes its environment
Kakadu National Park
Abiotic factors
Climate
Monsoonal- dry season, wet season
Sunlight
May affect cane toads
Important for plant growth
Soil
Wet season- good for toads to hide as it is full of nutrients
Biotic factors
Animals
Vital aspect of food chain
Serve as prey
Return nutrients to the soil
Examples: Northern quoll, Crocodiles
Plants
Producers
Vital part of food chain
Provide habitats
quolls living in logs
Savanna Woodlands
Moderately warm climate all year round
Wet season is very humid
Water is scarce during the dry season
Affect cane toads
Home to several species of large reptiles, mammals, and other species
Northern quolls have been found dead in the park
Reddened gums
Sign that they have been poisoned by eating cane toads
Cane toads
Organism defence
Some quolls have been taught by humans not to eat them
Quoll parents taught offspring to stay away
Black kite bird
Learnt to attack the toad's belly
Avoid poison glands on the back of the head
Dahl's aquatic frog
Able to eat tadpoles and live young
Some snakes have adapted smaller jaws
Unable to swallow large cane toads
Aren't affected by them
Meat ant is immune to the toxin
Freshwater crocodile has learned to eat just the hind legs
Keelback snake
Unlikely able to survive solely on cane toads
Can and do eat cane toads as they are tolerant to the toxin
Likely due to inbuilt characteristics rather than adaption to their presence
Adaptations
Individuals on the front lines show distinctive changes
Evolving by a process called spatial sorting
Fast toads have faster offspring
Growing longer legs
Travel faster and longer
10% of the toads develop spinal arthritis
Characteristics
Structural and behavioural features
Feed mainly at night
Nocturnal
Ground dwellers
Absorb water through their skin
Can breed all year round
Females lay up to 30 000 eggs at a time
Physiological features
Contain toxins that kill native animals
Glands on their shoulders
Bufotoxin
Acts on heart and central nervous system
Causes rapid heartbeat, hypersalivation, convulsions and paralysis
Toxins can be absorbed through membranes around the eyes, mouth and nose
Thrive in urban and disturbed areas
Breed quickly
Rapidly dominate and colonise an area
Voracious appetite
Eat a wide variety of foods
Depletes food source for other animals
Do not tend to hide and are usually targeted by predators
Predators are then exposed to the toxin
Impact on the environment
Initial concern was the threat to animal populations
Take shelter and habitats
One of the largest threats
Habitat loss for native amphibians
Adapting to wider environments
May spread to habitats currently unavailable
May affect cattle industry through increased disease
Predators are not adapted to their toxin
Disrupt food chains
Prey's prey will rise in population
Threatened species
Decline and extinction of several native predator species in the NT and Queensland
Pose a risk to both native animals and pets
Eat living insects in large quantities
Beetles, bugs, honeybees, ants, crickets
Eat larger animals
Native frogs, smaller toads, small mammals, snakes
Native frogs are particularly vulnerable
A food source for the cane toads
Competitor for other food sources
Northern quoll
Concern that it may be pushed to endangerment
Marsupial carnivore, and like the toad, will eat nearly anything
Vulnerable due to distinct breeding habits
Males die after the mating season
Goanna lizard
Eat the poisonous toad
Rainbow bee-eater
Lose up to one third of their nesting sites
Due to cane toad invasion and predation on eggs and nestlings
Ecological niche
The position of a species within an ecosystem, describing both the range of conditions necessary for persistence of the species, and its ecological role in the ecosystem.
Cane toad niche
Occupies niche of a ground dwelling predator as it eats insects and snails
2 hypothesis to explain the niche:
Empty niche theory: Cane toads fill an empty niche
Invaders occupy a vacant niche space in the recipient community
Competitive niche theory: Competes with other species for a niche
States that invaders overlap with native species in niche space
In KNP, occupies the niche of tree frogs as ground frogs don’t eat large prey
Broad environmental niche breadth
Boosted their ability to expand their distribution across Australia
Successfully colonised an empty niche among Australian anurans
Consumers
Consume other organisms within the Savanna Woodlands ecosystem
Population diversity
Selection pressures don't change
Population becomes more suitable and better adapted
Selection pressures change
Individuals that have adapted will survive and reproduce
Individuals that can’t adapt struggle to survive and reproduce
Individuals with successful adaptations
Increase
Change in population diversity