Patterns of Life Flashcards
What is biogeography?
occupies a space between several fields of research within biology (ecology, systematics, taxonomy, palaeobiology) and draws from environmental geography and geology- oldest discipline in biology
What made comparitive assessments of patterns of life across the globe possible?
Trade and the invasion of new territories by military forces
Name 2 of the 1st pioneers to notice the different patterns of life across the globe + what did they discover?
Comte du Buffon- noticed large animals of the old and new world were different
- Buffons law stating that different regions of the world were home to different species = principles of biogeography
Alexander von Humboldt- Travelled extensively and noticed the same thing applied to other animals and plants
OVERALL PATTERN = role a species plays in the environment is selected by the environment
What was the reason behind those observations?
Continental drift in 1915
What is convergent evolution?
the process whereby organisms not closely related (not monophyletic), independentlyevolvesimilar traits as a result of having to adapt to similar environments or ecological niches
Describe the process of continental drift
- Permian (300mya)- continents were combined into a single landmass called Pangaea
- Triassic (200mya)- split into 2 sections known as Northern Laurasia and Southern Gondwana caused by radioactive heating
- 120mya- a complete split had formed and the land masses started to move away
What did Alfred Russel Wallace develop?
A map of faunal kingdoms across the globe, based on changes in the distribution of mammals- has been updated but lines drawn still correspond to major continents
What are faunal kingdoms known as today?
Biomes
What are biomes and what is the pattern of distribution?
= correspond to different habitat types across the planet
- Warm + wet biomes run across equator
- Cold + dry biomes found closer to the poles
What 2 factors can be used to predict the distribution of biomes?
annual temp + rainfall
What was the trend identified by Humboldt?
altitude mirrors latitude- as you ascend a mountain in the tropics, you will pass through a similar sequence of biomes as if you were moving from the equator to the poles
Name all the different biomes and their chacteristics
Tropical rainforests
Savanna
Temperate forest
Temperate grasslands
Boreal forest
Tundra
Deserts
Describe the characteristics of a tropical rainforest.
- Highest species richness
- Predictable climate
- infertile soils- all nutrients are locked up in biomass
- layered- 1-2% of light reaches forest floor = increased competition for light and nutrients
- Average of 80mm of rain per month
Describe the characteristics of a Savannah
= recent biome, owning existence to evolution of C4 grasses
- C4 grasses + scattered trees = supports large herds of migratory herbivores
- Tree cover declines with rainfall until eventually leading to grasslands
- Hot seasonal climate- long dry period + occasional large fires, consequently = zone of feast and famine between wet and dry seasons
- Humans 1st evolved here
Twilight- Forks
Describe the characteristics of a temperate forest
- Located towards the poles
- Wild climatic range
- cooler climates = seasonal stress of winter = frosts
- deciduous trees lose leaves to reduce dehydration as growth is limited by low light + temp
- Inhabiting organisms must tolerate winter by hibernation/migration
- Rapid life cycles- due to short summers
- Many generalists feeders
natural field with cattle/sheep
Describe the characteristics of temperate grasslands
- entirely natural- no human involvement
- In the tropics
- Long dry seasons + lots of herbivores
- origins of civilisation + agriculture = modern crops were adapted from grasses in biomes
- Domesticated animals- grazing animals
Describe the characteristics of a Boreal Forest
- Cooler climates
- Few tree species = pest outbreaks e.g. Spruce budworm
- Mostly evergreen + drought adapted (e.g. spruce)- due to permafrost = frozen water unavailable to plants
- Slow decomposition = lots of stored carbon in soils
Describe the characteristics of a tundra
- short growing seasons = lack of tall vegetation = high dry winds
- Little organic matter- trees spread out
- Low creeping vegetation e.g. grasses, mosses
- ultimately end in polar deserts
Describe the characteristics of a desert
- Wide temperature range- cool to freezing point at night but can be very hot
- scare + unpredictable rainfall
- Species need to be opportunists e.g. weeds = grow rapidly + flower when rainfall occurs or need to be tolerators e.g. cacti- dont grow fast just tolerate dry conditions
- Low species richness + productivity
Why do more species exist (biodiversity) near the tropics and what it is known as?
=Latitude diversity gradient- biodiversity increases from poles to tropics:
- Tropics make up 40% of earth area
- Tropical forests are older than temperate forests so have had more time to get rich
- Warm and recieve plenty of rainfall- species more productive as recieve more energy
- Variety of niches = life more stable and drives specialisation
- Speciation occurs rapidly as plants and animals grow faster so can have more generations of off-spring = drives competiton and specialisation
What are ecoregions?
= patterns of diversity across the planet that includes idea of faunal kingdoms and biomes- each region describes an area of the planet with consistent species and habitat structure
How many ecoregions are there and why are they useful?
867 that vary in size and composition
- useful for conservation and form basis of biogeographical studies
What is the reason for low species richness in the polar biomes?
- occupy areas that were covered by ice only 20000 years ago
Why are we still considered to be living in an ice age and when did it begin?
2.6 mya
Glaciers spread from poles- at least 20 phases of ice formation and retreat
- duration of glacial periods exceed those without
What do ice ages lead to?
Promotes land bridges which connects land by reducing sea levels- lead to colonisation of UK
- very important in determining distribution of life
What happens during glacial phases?
- Biomes move around and change in size due to extent of glacial phases changes global climate as biomes shift to lower latitudes
= species richness is altered across the planet
What determines the composition of organisms found in freshwater streams/lakes and how mych of the overall area of the earth do they make up?
The land they are linked to- tiny fraction of earth area
What proportion of the earth is ocean?
2/3
Is sampling poorer on earth or in the oceans and why?
Oceans are very big and deep so not equipped enough to sample effectively but work in progress
What are oceanic ecoregions based on and why?
Planktonic communties in surface waters as they are easy to sample
What are examples of small crucial environments in the life cycle of many organisms?
Coastal habitats
Estuaries
Mangroves
What are ecosystem engineers?
= create or modify the habitats they are found in, but can also destroy it
- have a big impact on biodiversity in their habitat
Name an example of an ecosystem engineer and describe what they do
Beavers knock down trees and form pools which they feed from
= blocks river causing flooding upstream and drought downstream
Why are humans ecosystem engineers?
Development of agriculture and land-use change = we are transforming the entire globe
Why are biomes/ecoregions considered fictional?
describe how the world would look in the absence of humans
e.g. can measure rainfall and temperature in tropical rainforest to predict plants in the area but in reality lots of it has been chopped down by humans
How was the biosphere described in 1700 and how does this compare to the year 2000?
1700- 1/2 biosphere = wild = mostly regulated by natural processes
2000- 23% biosphere was wild and 20% semi natural- more than half of biosphere determined by human activity
What is the great acceleration?
Changes to biomes/ecoregions caused by human activity
What are anthromes and how are these managed?
human biomes- describe terrestrial biosphere in its human altered form
- fire, grazing, ploughing, irrigation + range of other interventions
Name + define the period we are living in now.
Anthropocene = period of earth history in which humans are the dominant force structuring the composition and distribution of life
