Migration & Biodiversity Flashcards
What is migration?
- Seasonal mass movement
- Long or short distances
- Can occur many times throughout an individuals life or just once
- Typically involves a switch from one habitat to another
Who migrates?
Animals from all major taxa: fish, crustaceans, amphibians, reptiles, insects, mammals
Examples of daily migration
Golden Jellyfish
- Symbiotic relationship with zooxanthellae algae
- Daily migration to sun their algae
Some fish, zooplankton
- Daily vertical migration
- Feed at surface at night
- Retreat to depths during day
How is the migration of amphibians and reptiles?
- Migrate to aquatic breeding ground (amphibians) or egg laying site (reptiles)
- Crossing roads is a major hazard
- In some locations, crossing tunnels or culverts have been constructed beneath roads to allow animals safe passage
What are migration stars?
- Bar tailed godwit
- Migrates from Australia/New Zealand to Alaska
- One non stop flight: 11,000 km, 9 days
Whats another migration stars?
- Bar headed goose
- Migrates over the Himalayas
From Southern Asia to summer breeding grounds in central asia - Extreme altitudes where there is less than 10% of oxygen found at sea level
- These geese have been seem flying over the top of Mount Everest
Why migrate?
- Seasonal changes in the local environment
Temp, drought, food availability - Changing needs at different life stages
- Move to a suitable habitat reproduction
E.g. many birds breed in the arctic in the summer
E.g. Pacific salmon live in ocean but migrate to freshwater streams to spawn
How do they prepare for migration?
- Migration requires a lot of energy
- Hyperphagia
Excessive appetite
Intense period of feeding prior to migration
Fat is stored for the long journey - Hyperphagia is observed in diverse species including birds, whales, insects, and caribou
E.g. birds can double their body weight before migration - Many species save energy by taking advantage of wing patterns and water currents
What is the shorebird stopover?
- Many species of shorebirds congregate in Delaware Bay, NJ
- Feast on horseshoe crab eggs
Plentiful
High in fat
Are the shorebirds in decline?
- Horseshoe crabs overgarvested
1992-1997 - harvested increased from <100,000 to > 2.5 million
2008 moratorium on crabs for bait
Estimated 60 years for recovery - Shorebirds in decline in last 2 decades in Delaware Bay
1.5 million to 350,000
How is the migration in birds?
- Not all birds migrate
Most N.A species do - Many migrate as far as the arctic
- Advantages of breeding in the arctic
Long daylight hours and very productive ecosystem
Ample resources
Space (reduces competition)
Relatively few predators - Migration routes generally follow set paths
Can be innate or learned - Some birds travel very fast
Bat tailed godwit (11,000 km in 9 days) - Others travel at a leisurely pace
Some warblers take 50-60 days to get from Central America to breeding ground in Canada - Birds navigate
Chiefly by sight (topographical landmarks)
Earths magnetic field
Sun and stars
What is the Arctic tern?
- Weighs only 100g
- Longest migration of any animal (70,000 km yearly)
Pole to pole: breeds in colonies north of the Arctic circle, spends the summer in the Antarctic - Over its lifetime (up to 30 years) can migrate 2.4 million km
Equivalent to three trips to the moon and back
How do the freshwater eel (fish) migrate?
- American eel
- Endangered species
- Lives in freshwater estuaries and spawns in the ocean
- A palmitic species
All members of the species mate randomly and are considered to form one large population - Eels are catadromous
- Live in freshwater (migrate to the ocean to spawn)
Coastal rivers of North America - migrate to the Sargasso Sea - Spawn at a depth of 300 m then die
- Tiny larvae begin the long migration back to the coast, growing along the way
Takes them 1 year to reach N.A estuaries
How do the salmon (fish) migrate?
- Most salmon are anadromous
- Spend adult lives at sea and return to freshwater to spawn
Atlantic salmon makes multiple runs throughout their lives
Pacific salmon make a single run and then die - Pacific salmon migrate downstream as juveniles
- Spend 3-4 years in the Pacific Ocean (growing)
- Return to spawn in the headwaters of its parent stream
How do salmon find their way back to parents stream?
- Guided by olfactory senses
- Can recognize particular door of their stream (caused by characteristic vegetation and soil)
- May navigate by the sun to find the right spot on the coast and then use olfaction
What is osmoregulation?
- Most freshwater fish will die if you put them in salt water and vice versa
- Euryhaline species can survive in a range of salinities
Freshwater: low salinity
Brackish water: medium salinity (found in estuaries where rivers meet the ocean)
Saltwater: high salinity - Two types of euryhaline species of fish:
Catadromous: migrate downstream to spawn
Anadromous: migrate upstream to spawn
How is the migration in mammals?
- Many marine mammals migrate
- E.g humpback whale (longest mammalian migrant)
Up to 8,000 km each way - Spend summer eating in Arctic or Antarctic
Store energy in blubber - Breed in tropical waters
- More difficult for terrestrial mammals than for birds, fish, or marine mammals
Terrestrial locomotion is more energetically costly than swimming or flying - Few terrestrial mammals migrate
Have a defined home range
Notable exception: caribou
What is biodiversity?
- Biological diversity
- Simple: a simple counting of the number of species in an ecosystem
What are the 3 levels of biodiversity?
Genetic
Species
Ecological
What is the distribution of species?
- Biodiversity is not evenly distributed across the earth
- High biodiversity
Tropical rain forests
Coral reefs - Low biodiversity
Arctic regions
What are endemic species?
- Distribution limited to small area
- E.g. Marine islands -> large number of endemic species
E.g. the birds, plants and insects of the Galapagos islands are found nowhere else - Vulnerable to extinction
- Conservation is generally directed towards regions with high diversity and lots of endemic species
What is the maintenance of biodiversity?
- Speciation is faster than extinction (on average) because otherwise we would have no biodiversity
- Biodiversity is created/maintained through speciation
- Speciation and extinction do not occur at steady rates throughout evolutionary history
What are the types of extinction?
Background
Mass
Anthropogenic
What is background extinction?
Gradual loss of species in a natural population as conditions gradually change
What is mass extinction?
- Loss of a large number of species during a short period of time due to a natural catastrophe (volcanoes, meteor impact, prolonged drought)
- Can eliminate nearly all (or all) species in a region
What is anthropogenic extinction?
- Loss of species due to human activity
- Rate of extinction is currently far above background levels
Are we in a 6th mass extinction?
- Some claim yes
- Extinction rates are well above natural background rates
8-100x higher - Others argue that we are in a biodiversity crisis but not a mass extinction
What are the threats to biodiversity?
- Habitat loss and fragmentation
- Invasive species
- Overexploitation
- Others (pollution, climate change)
What is habitat loss and fragmentation?
- E.g. coastal forests of Brazil
- If you destroy a species habitat, they will not do well
- Fragmentation happens in little patches
What are the effects of fragmentation?
- Cowbird is a brood parasite (lays eggs in the nests of other birds)
- When the patches of forests are small, Kentucky warblers are more likely to be parasitized by brown headed cowbirds
- Example of how fragmentation can put pressure on a species
What are examples of invasive species?
Exotic species
Invasive species
Invasion of new ecosystems is a natural process
Explain exotic species?
- Any species that is not native to the ecosystem
- Also called alien or non native species
Explain invasive species
Exotic species that has a negative impact on the ecosystem
Explain how invasion of new ecosystems is a natural process
Greatly accelerated through human intervention (purposeful and otherwise)
Why are invasive species the second most important threat to biodiversity?
- Cause diseases
- Act as predators or parasites
- Act as competitors
- Alter habitat
- Hybridize with local species
Whats an example of an invasive species?
- Brown tree snake
- Native to Australia, Indonesia
- Introduced to the island of Guam in the 1950s by cargo ships
- Eliminated 11 of the 12 native bird species endemic to Guam
Whats an example of an invasive species from here?
- North American species are invasive on other countries
- The Eastern grey squirrel threatens native populations of squirrels in Europe (and West coast of N.A)
What is the overexploitation of the passenger pigeon?
- 1914: Last passenger pigeon died at a Cincinnati zoo
- Once most abundant bird in N.A
- Flocks hundreds of km long
Containing millions (possibly billions) of individuals - Hunted to extinction
Habitat loss played a role as well - Migratory bird Treaty Act was established in 1918
Is biodiversity worth preserving?
- Moral considerations (is it our moral responsibility to protect nature?)
- Economic considerations (food resources, ecotourism, ecosystem services)
- Environmental quality
Loss of biodiversity is a sign of the poor quality of our environment
These species extinction are early warnings - Maintenance of ecosystem function
Species diversity stabilizes ecosystem function
More resilient to harsh conditions (more diverse systems are more likely to contain species capable of withstanding the stress)
