Lecture 3, Chapter 53 - Species Interactions

True or False: Age structure suggests whether a population is growing or shrinking. But to quantify growth, we first account for additions and losses. Because populations differ in size, we express change per individual using r. If r remains constant, population size changes exponentially.

True

Population grows most rapidly when N = K/ __

when N = K/2 (pg 1190 in the book has a good visual of this)

True or False: Age structure can tell us if a population is static

True

True or False: blue whales have a lower density than a population of harbor seal

True

What is the major difference between how we define terrestrial biomes vs aquatic biomes?

Terrestrial biomes are characterized by temperature and precipitation while aquatic biomes are characterized by nutrients and light availability

Interspecific Interactions

occurs between two species that live in the same area (community) and affects each other in 3 ways:

• +

• -

• 0

Predator

prey adaptations, cycles, and impacts of non-native predators on native prey

Name 4 times of predation and define each one

• parasitism - live closely within a single host organism, do not kill their host because they need it to survive

• parasitoids - a single female lays eggs in or on a host, larvae develops inside the host and eats it while it is alive, killing the organism as they grow up

• grazers (herbivores) - they only eat a portion of their prey without killing the entire organism (i.e. - cow eating grass)

• predators - kill their prey immediately after attacking them and consume multiple prey throughout their life

Name 4 strategies that prey/predators have evolved to “get the upper hand” on

• active + passive camouflage

• behavioral modifications

• structural defense

• chemical defenses

Passive Crypsis

color/patterns are fixed (organisms cannot change what they look like), adapted to blend in with their environment to help catch prey/avoid predation

1. color

2. pattern

3. texture

Animal Examples: lions, frogs, leaf-tailed geckos

Active Crypsis

color/patterns of themselves can change to fit environment

Animal Examples: chameleon, seahorse, octopus (changing its own color to sand))

Name an example of Structural Defense

cactuses developing spines and producing “helmets” in their body that protect against predation

Name an example of Chemical Defense

foxgloves (a type of flower) produces a toxic chemical to protect itself from being eaten

True or False: when a predator is introduced to an area where it doesn’t belong, it can wipe out local prey

True: these prey don’t recognize danger and the prey have no defenses so it would be easier for them to get wiped out

Predator-Prey Cycling in Nature (What does the graph show?)

experiment/graph shows that hares were caused by lynx predation rather than max carrying capacity

as hare population increases, it creates food supply for lynxes and the lynx population would grow/eat so many hares that the hare population plummeted (cycle repeats)

Why can’t predators hunt prey into extinction? (two reasons)

1. new prey move in → when predators eat prey in one specific area, new prey from other areas move in

2. safety zone/refugees → prey animals have hiding spots that predators cannot find

**Prey is always going to peak first and predators usually stagger behind them in graphs.

Parasite

an organism that feeds on the cell contents, tissues, and body fluids of the host while in/on the host organism

does NOT kill their host

Direct Transmission

can be transmitted directly from host to host (i.e. - human to human); can complete life cycle within one host

can transmission via: saliva, blood, surfaces (i.e. - Lice)

Intraspecific Competition

competition within a species (density based; mate to mate)

Interspecific Competition

competition between a species

Exploitative Competition

happens in interspecific competition; species compete over limiting renewable and non-renewable resources

no physical interaction between species required

Name one example of exploitative competition

• mussels and barnacles (shells) compete for space on rocky intertidal

• bald eagles and vultures compete to stand on the rocky land

Interference Competition

direct competition between organisms

• territoriality - fighting off other species from using certain spaces

• chemical warfare - killing/harming other species using chemicals

Give me an example of interference competition

• lions marking their territory (male-male competition)

• birds w/ their nests

• female bears w/ their cubs

Competitive Exclusion Principle

two species cannot coexist indefinitely if they are both limited by the same resource (they always have to compete against each other for it)

Fundamental Niche

the range of abiotic conditions a species could survive + reproduce in (w/ no competitors)

Realized Niche

the actual range of conditions (abiotic AND biotic) a species exists in (w/ predation, competition, resource scarcity)

Name 5 Long Term Competitive Outcomes of Evolution

1. character displacement

2. resource partitioning

3. mutualism

4. facilitation

5. symbiosis

Character Displacement

a trait shift that reduces the strength of competitive interactions between two species

Resource Partitioning

splitting of resources between competitor species

Mutualism

occurs when two species benefit each other

Facilitation

am umbrella term for interactions that benefit one species and have either no effect (commensalism) or a positive effect (mutualism) on other species)

Symbiosis

relationships characterized by close physical contact, w/ integrated bodies + physiology (can be mutualistic, parasitic, pathogenic)

Examples: bees and flowers

Name 4 Times of Mutualisms

1. generalists

2. specialists

3. obligate mutualists

4. facultative mutualists

Generalists

one species interacts with many species (i.e. - bees)

Specialists

one species interacts with one other species or only a small number of closely related species

only benefiting that one relationship

Obligate Mutualists

species that provide benefits to each other (+,+) and needs this interaction to persist

Facultative Mutualists

species that provide benefits to each other but do NOT need this interaction to persis

Ant-Acacia Mutualism

acacia trees provide nectar & shelter for ants while ants provide defense against herbivores for the trees

conditions that could cause the Ant-Acacia mutualism to break down:

• if there are no herbivores, ants are not needed

• providing nectar is costly (ants cannot get supplied)

Microbiome

most organisms have microbes (bacteria, fungi, protists) in their gut to help them digest food; help us digest otherwise inaccessible compounds and produce metabolities