PPT 16: Ecology
The Red Queen Hypothesis
(related to evolutionary arms race) - ex. toxic newts - ex. ants and fungi They both evolved together
Daphnia cyclomorphosis
- Abundance of predators induces metamorphosis to pointier, more robust (and less digestible) morphology - However, this response can be induced by any one of 3 or 4 predators, or by turbidity - No evidence that predators are reciprocally selected—they may have other food sources
community ecology
- All of these processes help shape communities, but it's important to remember that communities change over time - We will now examine how communities change over time, which is ____
cost of depressaria to parsnip plant
- In a controlled environment, more seeds made and set compared to the wild. - Making furanocoumarins costs the plant in terms of energy and resource allocation
cospeciation
- In general, the more closely related the host, the more closely related the parasites - Not a one-to one mapping—patterns differ in some places - Some hosts have multiple parasites, some parasites live on multiple hosts
example of mimicry
- Mexican Milk Snake looks just like texas coral snake but isn't poisonous - monarch vs. viceroy butterfly; viceroy is the bad tasting one
Anti-herbivore defenses of plants
- Plants in the carrot family (Apiaceae) contain many noxious compounds that have been shown to deter herbivorous insects -
energy
Every trophic level wastes ____ (10% rule) - eventually, all stored energy is lost as heat
succession
a gradual change in species composition in a community over time - primary succession - secondary succession
How does coevolution happen?
a. Mutualism b. Escalating "arms race" - Predator/prey interactions c. Co-speciation - Host/parasite interactions
Some expectations about arms races
a. We expect predators to increase as prey increases initially b. However, a boom in predators will decrease # of prey c. As prey becomes scarcer, predators die of starvation d. As predators become scarcer, prey populations rebound e. Cycle through this until stable (equilibrium) densities are reached
ecosystems
all living organisms, as well as non-living elements, that interact in a particular area
A. (for these Q's, look for a strong one to one relationship)
answer to slide 29
two types of mimicry
batesian - sheep in wolf's clothing; the mimic isn't poisonous or dangerous mullerian - Two or more species have warning coloration that is similar
symbiosis
close interactions between species - parasitism - mutualism - Commensalism - Predator-prey
co-evolutionary
Each participant in the _________ relationship undergoes natural selection, with the *highest fitness associated with genotypes that address the partnership.* Other selective forces such as food availability, sexual reproduction, etc still apply, but are of lower importance and so don't determine the direction and mode of selection the way the partnership does
population dynamics
What regulates population size? births and deaths Age structure determines whether or not a population is growing
parasitism
ex. bird leaving one of their eggs in another species nest so they don't have to waste energy raising their own offspring?? (European Cuckoo)
populations
groups of individual organisms that interbreed with each other
individuals
individual organisms
commensalism
interaction in which one species benefits and the other neither benefits nor is harmed - ex. cattle egrets (birds that stand on cattles heads) example of a community interaction
secondary succession
occurs when a community has been damaged, but soil remains - like primary succession but with a head start; begins with a disturbance that opens up part of a community to development and growth of species previously outcompeted by other species in the area. ex. fire occurs 1. pioneer species annual plants grow in 1-2 years grasses and perennials: 2-3 years 2. intermediate species grasses, shrubs, pines, young oak and hickory: 5-150 years 3. climax community mature oak and hickory forest: 150+ years
exponential growth
occurs when each individual produces more than the single offspring necessary to replace itself. According to realistic (and moderate) estimates of birth and death rates, a population of just 500 elk would grow to more than a billion individuals within 80 years and eventually cover the earth
B.
answer to slide 28
cospeciation in pocket gophers and lice
- Pocket gophers live in burrows throughout the plains and western states - Play a critical role in soil ecology through tunneling and enriching - Ectoparasitic chewing lice specific to gophers live on their body and eat debris and dead skin
The predator-prey arms race
- Prey are under strong selection to avoid predation - Predators are under strong selection to find sufficient food (so to be successful at prey capture) - If a predator specializes upon a single kind of prey, or a prey item has only one significant predator, this interaction may be the strongest selective force facing the organism ----> Having multiple prey/predators diffuses the effect any one interaction has on overall fitness
correlation related to Depressaria
- The most toxic genotypes co-occur with the most metabolically capable Depressaria - The detoxifying ability of the moth is selecting for the toxicity of the plant? - The toxicity of the plant is selecting for the detoxifying abilities of the moth?
colonizing community
- first step of primary succession - the first arrivals to a lifeless and soil-less area; they are good dispersers, but poor competitors, so they are gradually replaced
coevolution
- interactions between species are strong; - selection and evolution across species boundaries - selection driven by interaction between species - species are engaged in a "reciprocal adaptive response"
climax community
- longer living, larger species outcompete the initial colonizers and persist as a stable and self-sustaining community - taller, faster-growing trees outcompete the smaller trees
primary succession
- no soil exists - begins after a disturbance leaves an area barren of soil and with no life
intermediate communites
- part of secondary succession - a variety of species is present, including both colonizers and competitors a. mosses begins to grow and trap moisture, allowing the seeds of other plants to germinate b. small herbs arrive and shrubs grow, shading out the mosses and herbs c. small trees grow and outcompete the shrubs
logistic growth
- this accounts for environmental resistance - describes population growth that is gradually reduced as the population nears the environments's carrying capacity (sliide 68 chart)
ecosystem ecology
1. All ecosystems rely on a constant source of energy - ultimate source of energy is sunlight - energy flows in one direction only 2. Nutrient cycles recycle the atoms that make up every object in an ecosystem - chemicals are cycled through the ecosystem
energy flow within an ecosystem
1. primary producers - plants convert light energy from the sun into food through photosynthesis 2. primary consumers - herbivores are animals that eat plants 3. secondary consumers - carnivores are animals that eat herbivores 4. tertiary consumers - top carnivores are animals that eat other carnivores
Depressaria
= insects that spend most of its life on a single plant; preferentially eats reproductive tissues (flowers and seeds)
mutualistic relationships
A form of symbiosis Both partners derive some benefit from the interaction Typically fairly specific - Otherwise, force of selective pressure may not be sufficient
Malthus' "Struggle for existence"
At the point where population size outstrips resource production, there are only two alternatives: find the means to expand the resource pool, or DIE.
1.
Choose the answer most correct: In a series of isolated populations of garter snakes what would you expect about their resistance to newts' toxins if you know that in some locations newts are either present or not and that their toxicity varies: 1. Resistance would be variable but will show a geographic pattern 2. Resistance would be equal in populations with and without the newts because the snakes are the same species 3. Resistance would be randomly variable 4. 1 or 2 5. 2 or 3
Phylogenetic coevolutionary hyotheses
Cospeciation: Host and parasite lineages diverge in tandem ("classic coevolution") - slide 50 tree
Cost to Depressaria--Detoxifying plant tissue
Depressaria detoxifies plants metabolically The ability to detoxify furanocoumarins has a genetic basis several genes encode elements of the metabolic pathways The metabolic processes are expensive in terms of energy
population growth
Exponential Growth occurs under ideal conditions - growth rate = births - deaths - population grows at a rate proportional to its size
populatin growth
Exponential growth is met by environmental resistance - limited resources, accumulation of wastes, increased competition or predation Carrying capacity: max # of individuals the habitat can support indefinitely - growth slows then stops when approaches carrying capacity
B.??
How can we best explain why a king snake looks like a coral snake? A. The coral snake mimics the king snake B. The king snake takes advantage of predators associating coral snake coloration with being venomous C. Bright colors advertise that the king snake is venomous D. The king snake looks completely different from the coral snake E. Both A and B are true
coevolution
_____ is different than everything we have talked about before because we are talking about interactions between species, not interactions within or between populations of the same species
selective regime
_____ is not set by the physical components of the environment, but by the biological interactions occurring within the ecosystem
community ecology
Populations interact to form communities
ecology
The study of the interactions of organisms with their environment - Individual - Population - Community - Ecosystem ---- biotic ---- abiotic
Depressaria and variation
There is variation among Depressaria in terms of the ability to detoxify the furanocoumarins There is variation among parsnips in terms of the amount of furanocoumarins
must show specificity!
To be co-evolution, the predator-prey relationship must be the primary selective force, and there must be reciprocity in the response aka ____
communities
populations of different species that interact with each other within a locale
trophic level
position in the food chain, relative to energy source
2. arms race
slide 52 graphs provide evidence for what type of relationship: 1. Mutualistic 2. Arms race 3. Co-speciation 4. None of these
energy
study slide 60
predation
when one organism feeds on another -> exerts strong selective pressure on prey - camouflage - warning coloration - mimicry - mechanical defense - chemical defense - behavioral defense