Ecology Lesson 5

Question 1

Community

Answer 1

Set of species in a specific location

Question 2

Community Functions

Answer 2

• Species interactions (ie. competition)
• Energy and nutrient flows and what direction they flow.

Question 3

Community Structure

Answer 3

• Species richness (number of species). Diverse?
• Composition (relative abundance of species). Is there rare or common species.

Question 4

Community dynamics

Answer 4

• Change in structure or function over time (abundance and interaction, etc.)

Question 5

Trohic interactions

Answer 5

All - and +. Related to feeding. Transfer of energy from one to another.
* Predation
* Herbivory
* Parasitism

Question 6

Food webs

Answer 6

Represent trophic interactions. The arrows show the direction of energy flow. Made up of food chains in the web. Read from bottom to top. Bottom is the primary producers and top is usually humans. Very complex and dynamic. They can generalize groups, ie. birds.

Question 7

Trophic Level

Answer 7

Vertical position in the food web.

Question 8

Tundra food web

Answer 8

Herschel Island, North Yukon and Mostly short food chains. We can compare food webs in different ecosystems. It has lots of primary producers and lemmings.

Question 9

Collared lemmings

Answer 9

eat most plants, eaten by most predators – “important.” It connects the species together. If you lose it, it turns into two food webs.

Question 10

Species with a large impact

Answer 10

Some species play a disproportionate role in
the food web.
Domaint species
Ecosystem engineers
Keystone species

Question 11

Domaint species

Answer 11

Large impact due to high biomass. There are a lot of them.

Question 12

Ecosystem engineers

Answer 12

Large impact because they alter the physical environment. ie. beavers make dams.

Question 13

Keystone species

Answer 13

• Large impact despite low biomass and abundance.
• Usually predators, have control over species that they prey on.
  Otters

Question 14

Top-down control

Answer 14

Higher trophic level reduces abundance or
biomass of lower trophic level. The impact on one trophic level on the trophic level beneath it. More herbivores = less plants.

Question 15

Trophic Cascade

Answer 15

Impact of top predators extends to lower trophic
levels. It impacts plants despite not directly eating them. It’s why predators are important in ecosystem structure. Predators=less herbivors=more plants.

Question 16

Sea otters example (in BC)

Answer 16

1960- no sea otters, so lots of sea urchins so less kelp. Top-down control of U and K.

1970- Sea otters return. Less urchins. Top-down control of O and U

1970-The more sea otters the more kelp (good because they provide habitat and shelter for many species). Trophic Cascade.

1990 (in alaska)- orcas started to eat sea otters, so more urchins, less kelp.

Question 17

Sea otter impacts on community

Answer 17

1. Fewer herbivores
   * Sea urchins, starfish
2. More kelp
   * More productive
   * Physical structure
   * Fish species richness

Question 18

Atlantic coast urchin example

Answer 18

The Atlantic coast has no sea otters and not as big kelp beds.

Historically it was top-down with large predatory (other fish that act as each other) fish then sea urchins then kelp.

Then a trophic casacade when overfishing occurred because more sea urchins and less kelp.

Then in 1980s the urchins got a disease then more kelps. But then the urchins recover, so less kelp. (Alternating communities)

Question 19

Alternating communities

Answer 19

The sea urchins where it fluctuates between these two kinds of ecosystems. It depends on the water temp, as the pathogen that kills the urchins is I’m the warm water.

Question 20

Regime shift

Answer 20

Abrupt shift to a very different and persistent community. They may or may not recover. ie. kelp to barrens and corals to marcoalgaes.

Question 21

What causes a regime shift?

Answer 21

Usually external drivers:
* Removal of keystone species
* Arrival of disease
* Climate change
* Nutrient inputs

Question 22

Bottom-up control

Answer 22

Lower trophic level controls abundance or biomass of
higher trophic level
* E.g. primary producers limit herbivore biomass

Question 23

Top-down critical points

Answer 23

• Top predators frequently exert top-down control
• Without predators, herbivores often have strong
  impacts on primary producers.

Question 24

Top-down Applications

Answer 24

1. Wildlife management in absence of top predators (want to reintroduce them to get the ecosystem back to normal).
2. Management of insect pests (use natural predators).
3. Management of natural resources (ie. limiting on fishing to ensure the ecosystem doesn’t switch to a different state).

Question 25

Ecosystems have an impact on what?

Answer 25

The rate of transmission of zoonotic diseases.

Question 26

Zoonotic disease

Answer 26

Animals to humans.

Question 27

What is Lyme disease?

Answer 27

it's parasitism. * Caused by a spirochaete (bacterium) Borrelia burgdorferi * Pathogen can cause fever, joint pain, arthritis * Bulls-eye rash.

Question 28

How do you get the Lyme pathogen?

Answer 28

Tick bites. They live in grassy ecosystems. * Black-legged tickn (Ixodes scapularis). Also called deer tick. Only adults bite humans. * Enlarge during feeding. Ticks carry it (they are a vector).

Question 29

Ticks in NS

Answer 29

The cases are increasing. The range is expanding.

Question 30

Transmission of Lyme Disease (the two types)

Answer 30

Pathogens must move between hosts. Ticks get the pathogen by feeding on an infected host When the tick feeds again, it may pass pathogen on to new host Humans are just accidental hosts. * Direct – pathogens move from one host to the next (person to person). * Indirect – pathogens use another organism (vector) to help them move (they need to tick).

Question 31

Tick meals

Answer 31

Larva - Birds and small mammals Nymph - small and large mammals Adult - Deer

Question 32

Do newly hatched tick larvae have Lyme disease?

Answer 32

No, they have to pick it up from one of their hosts.

Question 33

How long have pathogen and ticks have been around?

Answer 33

Pathogen (Borrelia burgdorferi) * In N. America for >60,000 years Ticks (Ixodes scapulari) * In NE USA for >10,000 years

Question 34

Lyme disease historically

Answer 34

* Lyme disease common when Europeans first colonized North America * Incidence declined dramatically during 1800s * Increased again in late 1900s

Question 35

Lyme disease timeline

Answer 35

* Pre-1700: Forest and deer abundant * 1830: Peak of forest clearing (25% left) (so no deers) * 1850: Farm abandonment * 1910: Abandoned fields * 1930: Forests recovering * 1960s: 75% forested

Question 36

Deer recovery in Connecticut

Answer 36

1896: ~12 deer Today: 150,000 deer

Question 37

Monhegan Island, Maine Example

Answer 37

It originally had a lot of ticks so they Eradicated deer then Lyme disease disappeared. Deer have impact on tick abundance and transmission to humans.

Question 38

Small mammals limit tick abundance

Answer 38

More mice -> more infected ticks -> more cases of human Lyme Factors that influence white-footed mouse abundance affect incidence of Lyme disease – coyotes vs. foxes. Coyotes have a negative impact on foxes=more mice.

Question 39

How does Lyme disease spread?

Answer 39

* Migratory birds move ticks to new locations. * First infected tick in NS found on migratory bird (Bon Portage Island, 1999). Eventually enough ticks arrive to establish populations in new areas.

Question 40

Forest recovery on ticks

Answer 40

* Deer recovery * Tick recovery * Number of ticks hitchhiking on birds increases

Question 41

Ecological interactions are key to understanding disease dynamics?

Answer 41

1. Deer necessary for ticks – forest recovery led to more deer. 2. Small mammals limit tick numbers (top-down). 3. Migratory birds facilitate tick dispersal (they move them).

Question 42

Climate change and Lyme disease

Answer 42

* Climate must be warm enough for tick survival and reproduction. * As climate warms, black-legged tick range predicted to expand.