Origins of Biodiversity Flashcards
What is speciation?
Gradual change of a species over a long period of time
> When pops. of same species are separated, get cannot interbreed
If the environments they inhabit change, they may start to diverge+new species forms
How can humans speed up speciation?
- artificial selection of plants + animals
- genetic engineering
Name 3 pieces of evidence that support Charles Darwin’s Theory of Evolution (1859)
- fossil records
- discovery of the structure of DNA
- mechanisms of mutations
What is the process of natural selection?
- each individual has a particular set of inherited genes + mutations
- each will be slightly differently adapted to its environment
- resources are limited for any pop. and there will be competition for these
- eg a giraffe w a slightly longer neck can reach tree leaves that are out of reach to others + get more food
- these small diffs mean some individuals will be more successful, they will survive to breed more than others + so pass their genes onto next generation
- over time these changes show + whole pop gradually changes
How may populations be isolated ?
Geographically
- mountain, water, island
- physical barrier will split gene pool
Reproductive
- mating seasons not synchronised
- their flowers mature at diff times
What happened to the large flightless birds found on Gondwana?
- Large flightless birds only occur on continents that were once part of Gondwana (Africa, Australia, New Zealand, South America)
- However, because Gondwana split up a v long time ago, the large flightless birds are not closely related
What are land bridges?
Allow species to invade new areas.
e.g. North and South America were separated for long time + therefore have different species. They are now joined by a recently formed land bridge of Central America, which allows species for move North // South. e.g. Bears moved from North to South
How has continental drift resulted in new and diverse habitats?
- During drifting over the globe, the continents have moved to different climate zones
- The changing climatic conditions + therefore food supplies forced species to adapt + resulted in an increase in biodiversity
e.g. Antarctica once had a tropical climate, but as moved southward, the forest gradually disappeared
Name a conservative plate boundary
San Andreas fault line, California
Name a constructive plate boundary
The mid-Atlantic ridge where the plates are moving apart
Name 2 examples of destructive plate boundaries
- Collide and be forced upwards as mountains e.g. Himalayas
- Collide and oceanic plate sinks under lighter continental plate creating subduction zone. This creates land bridges + new niches
Name two domesticated animals that fulfil similar roles
Llamas in South America
Camels in Africa // Central Asia
- They are distant cousins
- Both were domesticated 5000years ago + used by animals as pack animals + for meat + milk
- Suggests that these areas were connected in the past
How many years ago did the Earth form?
The Earth formed about 4.6 billion years ago
What is background extinction rate?
- The natural extinction rate of all species
- It is one species per million species per year
- This is estimated from the fossil record because we dont know how many species there are alive today
How many mass extinctions have there been? How do we know this?
5 major ones spread over 500 million years
We know this from
- the fossil record when suddenly fossils disappear from the rock strata
- there is abrupt increase in rates of extinction
What has been the cause of mass extinctions in the past?
- rapid change in climate
- natural disaster e.g. volcanic eruption
What is the Holocene extinction event ?
The sixth mass extinction that we are now in.
Began at end of last ice age when large mammals like the woolly mammoth + sober-toothed tiger became extinct probs through hunting
The rate has accelerated in last 100 years, perhaps due to human-induced climate change
How many mammal species are listed as critically endangered or the ‘living dead?
169 mammal species
‘Living dead’ species are ones w such small pops. there’s little hope they will survive // they have lost a species they depend on e.g. pollinator insect for flowering plant
What was the K-T extinction?
- happened 65 million years ago
- when dinosaurs became extinct
- most large animals + small oceanic plankton died out
- most small animals+plants survived
What were the 3 causes of the K-T extinction?
- Volcanoes of the Deccan plateau erupted for 1million years at time of extinction
- meteor impact putting huge amounts dust into atmosphere: evidence is Chicxulub crater in Mexico
- Result of climate change over long period // dust from eruption + meteor impact would have blocked incoming solar radiation so plants couldn’t photosynthesise
What proportion of all plant and animal species went extinct between 1985 and 2015?
Estimated 25%
What are weedy species?
- The organisms that are successful in the environments we create (urban rats, domesticated animals…)
- Many weedy species will probably thrive in the current mass extinction
What is the difference between the previous mass extinctions and the current one?
Previous mass extinctions due to abiotic causes over extended periods of time
Current mass extinction is anthropogenic so has a biotic cause + is happening over a few decades
In what ways are humans the direct cause of ecosystem stress?
Transform the environment
- cities, roads, industry, agriculture
Overexploit other species
- fishing, hunting + harvesting
Introduce alien species
- which may not have natural predators
Pollute the environment
- killing species directly or indirectly
What is the Living Planet Report?
- WWF produces a periodic report on the state of the world’s ecosystems.
- Measures trends in Earth’s biological diversity
- 2012 report saw decline in overall living planet index of 30% between 1970 + 2008
- but also improvement in temperate oceans + terrestrial ecosystems
