Lecture 20: Paleoecology

Question 1

Paleo:

Answer 1

-older or ancient, often relating to the [geologic] past

Question 2

Ecology:

Answer 2

-relationships of organisms to one another and to their physical surroundings

Question 3

Paleoecology

Answer 3

the study of past ecological communities

Question 4

Paleoecology (extended definition)

Answer 4

the study of past composition and distribution of past ecosystems, and their changes through time on scale of decades to hundreds of millions of years.”

Question 5

Two Major Types of Paleoecology:

Answer 5

1) Quaternary Paleoecology: Last ~2.8 million years

2) Deep-time Paleoecology: Based on fossils from pre- Quaternary sediments over a wide range of timescales

Question 6

“Modern” Ecology is Taxonomically resolved whereas paleoecology is…

Answer 6

-temporally resolved

Question 7

Examples of questions modern ecologists can answer:

Answer 7

• Where (in space) do changes in the environment occur?
• Which species are most affected after spatial disturbances?
• How do species distributions shift over space (e.g., landscapes)?

Question 8

Examples of questions paleoecologists can answer:

Answer 8

• When (in time) did changes in the environment occur?
• Which species are most affected after temporal disturbances?
• Did the environment change when species were affected?
• How fast do changes take place (what are rates of change)?

Question 9

most common method, longer record, resolution varies (years represented by each sample)

Answer 9

Piston Cores

Question 10

less common, shorter core (~one meter), layering is preserved, fine examination is possible

Answer 10

Freeze Cores

Question 11

The Paleoecological “Proxy”

Answer 11

Physical, chemical, or biological material preserved within the geologic record.

Question 12

Physical Proxies

Answer 12

• Characteristics like sediment composition, texture, color, density, magnetism, etc.
• Changes in physical properties help infer past climate conditions.
• Environmental change, driven by climate, can alter physical properties of sediments in predictable ways.

Question 13

Terrestrial Biological Proxies

Answer 13

• Remains of living organisms in terrestrial environments.
• Distribution or organism controlled by temperature, moisture, competition, etc.
• Presence in a sample allows scientists to make inferences about past climate and environmental changes.
• Includes pollen and spores, plant microfossils, charcoal, middens, phytoliths, and even lepidoptera scales

Question 14

Direct proxy example

Answer 14

(e.g., gases trapped in glacial ice)

Question 15

Indirect proxy example

Answer 15

(e.g., biological proxy)

Question 16

Tree rings are a special kind of biological proxy:

Answer 16

changes are recorded in annual growth layers.

Question 17

Aquatic Biological Proxies

Answer 17

• Remains of living organisms in aquatic environments.
• Can provide information on parameters in marine or freshwater environments (e.g., salinity, temperature, nutrients, water depth, and substrate).
• Includes foraminifera (“forams”), mollusks, ostracodes, diatoms, corals, radiolarians, and dinoflagellate cysts (!!).

Question 18

Chemical Proxies

Answer 18

• Composition of shells of aquatic organisms is affected by the chemistry of the water in which they form (and water is influenced by temperature and precipitation).
• Organisms that secrete sequential layers (e.g., mollusks and corals), these layers archive change over the lifespan of the animal.
• Includes stable and radioactive isotopes, elemental composition, and organic biomarkers among others.

Question 19

Types of proxies include:

Answer 19

• Physical Proxies
• Terrestrial Biological Proxies
• Aquatic Biological Proxies
• Chemical Proxies

Question 20

How do we know how old things are?

Answer 20

• qualitative approach

- quantitative approach

Question 21

The isotopes of carbon are commonly used for dating fossils (younger than ~_________).

Answer 21

50,000 years old

Question 22

14C is …

Answer 22

“unstable” or “radioactive”

Question 23

rate of decay from laboratory experiments

Answer 23

(“half-life”)

Question 24

12C is referred to as

Answer 24

“stable”

Question 25

Older remains have______Carbon 14 than younger remains

Answer 25

less

Question 26

Paleoecological Proxy

Answer 26

preserved materials that can be representative of past climate or the environment