The Galapagos Islands are a volcanic archipelago of 13 major islands located in the Pacific Ocean approximately 1 000 kilometres west of Ecuador in South Am...

(a)(i) An invasive species is a non-native organism that has been introduced to an area where it did not previously exist and which spreads rapidly, causing harm to the native ecosystem and its species [1]. The damage occurs because native species have not evolved defences against the invader, and natural predators or competitors that would normally keep the invasive species in check are absent.

(a)(ii) Two ways invasive species could have been introduced to the Galapagos [1 each, max 2]:

1. Accidental introduction: Animals such as black rats arrived on ships visiting the islands, escaping from cargo holds or stowing away in food stores [1].
2. Deliberate introduction: Goats were brought intentionally by early settlers as a source of food and milk, then escaped or were released into the wild where they reproduced rapidly [1].

Other valid answers include: invasive plant seeds carried on tourists' clothing or equipment, or plants brought intentionally for agriculture that then escaped into the wild.

(b) Relationship between invasive and native plant species on Island A:

1. As invasive plant species on Island A increased from 45 to 148, native plant species decreased from 280 to 190 [1].
2. This shows a negative correlation, suggesting that the invasive species are displacing native species by outcompeting them for essential resources: sunlight, water and soil nutrients [1].

Note that on Island B (uninhabited, restricted access), invasive species increased more slowly (12 to 28) and native species declined less (195 to 178), demonstrating that human activity accelerates the introduction and spread of invasive species.

(c) Black rats have affected ground-nesting bird populations through:

1. Predation on eggs and chicks: Black rats prey on the eggs and newly hatched chicks of ground-nesting birds, reducing the number of young that survive to adulthood [1].
2. Population decline: Over time, this increased predation causes the population of ground-nesting bird species to decline because fewer individuals successfully reproduce in each generation. The birds evolved on islands without mammalian predators, so they have no behavioural defences against rats [1].

(d) One method of controlling invasive animal species on islands [1 for naming, 1 for describing how it works]:

Systematic hunting: Trained dogs and skilled hunters locate and remove feral animals from the island systematically, working across the terrain in a planned grid pattern to ensure every area is covered [1+1].

Other valid methods include: bait stations containing targeted poison (such as rodenticide for rats) placed across the island, or baited cage traps to capture live animals for removal.

(e) Eradication is harder on large inhabited islands because:

1. Complex terrain: Large inhabited islands have more complex terrain with more hiding places for invasive species, making it much harder to locate and remove every single individual. Even one breeding pair left behind can re-establish the population [1].
2. Human presence limits methods: The presence of human settlements, farms and domestic animals means that some eradication methods (such as aerial poison drops or broadcast baiting) cannot be used safely near people and livestock [1].

(f) Captive breeding programmes contribute to managing biodiversity through:

1. Protected rearing: Young animals are raised in predator-free enclosures where they are safe from invasive species such as rats, dramatically increasing their survival rate during the most vulnerable early stages of life [1].
2. Population recovery: The programmes help maintain and increase the population size of endangered species such as giant tortoises, preventing them from falling below the minimum viable population threshold needed to avoid extinction [1].
3. Genetic diversity: By releasing captive-bred individuals into the wild, the programmes help maintain the genetic diversity of wild populations, making them more resilient to disease, environmental change and future threats [1].

(g) Managing biodiversity on isolated islands is particularly important because:

1. Endemic species: Many species found on the Galapagos are endemic, meaning they exist nowhere else on Earth. Giant tortoises, marine iguanas and Darwin's finches are found only on these islands [1].
2. Irreversible loss: If these species become extinct due to invasive species or habitat loss, they will be lost permanently with no possibility of reintroduction from another location. There is no backup population anywhere in the world [1].

(h) One way tourism both benefits and threatens biodiversity:

1. Benefit: Tourism generates income that can be used to fund conservation programmes, scientific research and invasive species eradication efforts on the islands [1].
2. Threat: Tourists can accidentally introduce invasive species by carrying seeds or small organisms on their clothing, shoes or luggage. Increased visitor numbers also cause physical disturbance to sensitive habitats and wildlife [1].

(i) International cooperation is needed because:

1. Controlling introductions: The Galapagos belong to Ecuador, but invasive species can arrive on ships and aircraft from many different countries. Controlling introductions requires cooperation with international shipping and aviation authorities [1].
2. Shared resources: Funding for conservation comes partly from international organisations and donations, and scientific research involves researchers from many countries working together. The global significance of the Galapagos means their protection is an international responsibility [1].