Lecture 2: Evolution by natural selection 3

Question 1

Flightless bird

Answer 1

Increasing isolation of species with a common ancestor over 100 million years

pangea found from diff contients

Question 2

Allopatric speciation

Answer 2

speciation due to geographical separation of populations

Question 3

Sympatric speciation

Answer 3

Sympatric = speciation within a population due to reproductive isolation, e.g. from variation in resource availability within a location or niche differentiation

Question 4

Parallel evolution

Answer 4

Sometimes a bifurcation in an evolutionary line will lead to very similar life history traits as species evolve to fill ecological niches
• Placentals and Marsupials separated
in the late Cretaceous (100 – 70 mya)

Question 5

Movile cave

Answer 5

Cave system (12,000 m2) in Romania completely isolated from the rest of the world (no light, no interactions with other species)

• Discovered by a team of geologists in 1986
Groundwater ecosystem powered by chemosynthesis rather than photosynthesis – the atmosphere is poor in oxygen (7-10%), high in carbon dioxide (2-3.5%) and methane (1-2%). Sulphurous springs seep into the cave

• Oxygen provided by sulphur-oxidising micro-organisms that form mats across cave walls, sediments and water surface – bacteria and fungi are the main sources of organic matter (primary producers)

Question 6

Caves invertebrate

Answer 6

Invertebrates are found in the caves, which have evolved into separate species after being isolated from the ancestors for thousands of years

• All of these species have abaptations, including the loss of pigmentation, the loss of sight, and the ability to survive on bacteria and fungi; or, in the case of predators such as leeches and water scorpions, the invertebrates themselves
• 46 species so far found in the ecosystem (terrestrial and aquatic), of which 31 (or 33?) are endemic to this single cave

Question 7

As continents were drifting

Answer 7

While the continents were drifting, the climate of the earth was also changing (on much shorter time scales), changing the suitability of particular individuals to given locations

• The present distribution of species is largely due to the legacy of climate change
• The proliferation of land plants led to reduced CO2 and global cooling in the Carboniferous period
• Evidence from ocean cores suggests that in the Pleistocene there were as many as 16 ice ages, each lasting 50,000-100,000 years, with interglacials of 10,000-20,000 years. We are in an interglacial now – all species have evolved through ice ages and are currently in an extreme warm event!

Question 8

Climatic speciation

Answer 8

Tetracanthella arctica Cass.
• This insect lives in soil surfaces and clumps of moss
• Found in arctic regions (Iceland, Greenland, Arctic Canada) and in three other places: Pyrenees (France/Spain), Tatra Mountains (Poland/Czech Republic) and the Carpathians, at altitudes of around 2000 m
• A relict of a time when Europe was covered by ice – although why not found in the Alps?
• There has also been some evolution since this time (e.g. number of ocelli)

Question 9

Glaciation and climate change

Answer 9

Over large temporal scales climate has been highly variable due to the changing positions of oceans and continents, glaciers being produced, and mountains etc. providing geographical barriers

• During the last 2 million years repeated cycles of glaciations have occurred at high latitudes and at high elevations
• Many existing patterns of diversity can be attributed to this – and many areas are still recovering – e.g. from the last ice age 11,000 years ago

Question 10

Changes in geographic range

Answer 10

One possible explanation for the notable difference in diversity of temperate forest trees in Europe (lower) as opposed to North America (higher) is the position of the mountain ranges