lecture 20 Flashcards
Chimney Swift (Chaetura pelagica)
- Part of the guild of Ariel insectivores
- Ariel insectivores are in trouble (43% decline over the last 50 years)
- Chimney swifts live in chimneys, they breed in there to stay safe they make nests in the walls of chimneys
- Don’t land for the entire time that they overwinter in Africa
- actually used as a chimney isn’t
conductive to bird life - Guano 1928-1993
- Dissect the debris
- found all sorts of insect parts
- can use to see how the diets of chimney swifts has changed
Paleoecology
- Paleoecology deals with populations, communities, and ecosystems of the past
- reconstruct historical ecosystems to understand them.
- “Paleo-” is the Greek root for “ancient”
ex. Tree ring analysis helps us to understand growth conditions in the past
- Uses fossils and other kinds of data to
reconstruct historical ecosystems - By studying past ecological changes, we
can better anticipate the future
Two key principles of paleoecology:
- Uniformitarianism: if we understand how
organisms respond to environmental factors today, we can infer features of past communities and ecosystems
ex. If we know how quickly a particular autotroph can cycle water
we can dig up past plants and make inferences
- Superposition: sequence of sedimentary deposits are arranged with the oldest at the bottom and the youngest at the top
- oldest bottom newest top
Fossils
- Use fossils to gain insights about communities and ecosystems where, like in the past
ex.
Fossil evidence shows an extinct camel browsed these ancient far-northern forests 45 mya - suggests very different landscape and organisms
ex.
Fossilized trees shows arctic forests during the
Eocene epoch 45 mya (was part of a lush tropical forest now Arctic)
ex.
Fossils show a species of giant beaver lived on
Ellesmere Island approximately 4 mya
Drawings on a chalk wall
- Infer information of past ecology
Environmental changes
- Allows you to infer more information about more than one organism
- Just 15,000 years ago, most of Canada was
covered in ice - Paleoecologists explore ecological
changes since the last glacial retreat
using several “natural archives”
Dendrochronology
Dendrochronlogy is the paleoecological study of tree rings
* Tree growth is seasonally variable, producing annual rings
* Larger xylem vessels during fast growth
* Ring width is used to infer information about what the environment was like.
- It’s influenced by temperature, drought, pests
WE don’t have to cut down trees to use dendrochronology:
- measured with an increment borer
- Surface of the core sanded so there’s no wood grain
* Look at rings with image analysis software
Interpretation of tree rings
Ring width reflects growth conditions of the past
* Narrow rings reflect dry or cold year
- can also be different colour if there was lots of ash in the air
* After volcanic eruptions, narrow tree rings are often global
- Shrunken rings could be due to flooding, size can confirm by historical records of that time. Use this info to study trees before historical records were available.
* Fire scars on tree rings tells us of the historical periodicity of fire
Long tree ring records
- Trees can live for centuries
- Combining information from
preserved dead trees in lake
sediments or buildings, tree-
ring records can be made for
longer periods - Through cross-dating,
dendrochronological records
extend up to 10,000 years
ago - can reconstruct ecosystems from thousands of years ago using these techniques
Growth rings in other organisms
Incremental growth can be used similarly for hard-bodied corals and mollusks, and fish otoliths (inner ear bone)
- Can be measured and see how much organism grew per year
Sediments
Sediments accumulate in oceans, rivers, lakes, etc.
* Algae, animal remains, pollen grains are preserved in the sediment
- Autochthonous material: material from inside lake
Allochthonous material: outside lake
* Provides a historical record of organisms
present at time of sedimentation (in the past)
and gives info about abiotic sediments
Sediment cores
Sediment cores collected from lake bottoms
* Short cores to study recent centuries: glass tube
* Long cores to study periods back past the end of the last Ice Age: used to sample bottom of ocean
- deeper you go, older time you study
- Dated by counting seasonal layers, carbon dating or based on radioactive isotopes
- Measure how fast it accumulates sediments
- Pick away at dirt extract things you’re interested in
Palynology
- Palynology is the paleoecological study of pollen
- Unlike most plant tissue, pollen resists decomposition - they are designed to be supper strong.
- Can identify the pollen to see what autotrophs were found around the lake
- Large quantities of pollen in wind-pollinated species
- Presence of pollen grains is an indicator of vegetation
- Some pollen is transported very long distances
- All inferred from tube of mud and some pollen grains
Diatoms
Tiny photosynthetic things that produce a layer of sylica around them, left as a skeleton
- every particular species of diatoms has its own niche
Thousands of diatom species, each with an
optimum temperature, pH, and nutrient level
* Siliceous cell walls preserve very well
* Diatoms in lake sediments tell us about
past environmental factors conditions in
that lake
Environmental optima & tolerances
Each species has optimal conditions
* Presence of a species gives indications about
environmental conditions
* Species composition in sediments tells us about past conditions
- Every PH is the perfect growth environment for different species of diatoms
- You then know the pH of the lake of a species that was deposited
We don’t really care what atoms were there
we care about their niches
As long as you know what diatoms prosper at each point, you can figure out abiotic influences at that time by their niche
