Chapter 14: Ecology Flashcards
population ecology
study of growth, abundance, and distribution of populations
1. Size: N, total number of individuals in population.
2. Density: total number of individuals per area or volume occupied.
3. Dispersion: describes how individuals in a population are distributed; may be
clumped, uniform, or random.
4. Age structure: description of the abundance of individuals of each age. 3 2 1 (%
male) 0 (% female) 1 2 3 with horizontal bars for each age group.
5. Survivorship curves: how mortality of individuals in a species varies during their
lifetimes.
a. Type I: most individuals survive to middle age and dies quicker after this
age (human).
b. Type II: length of survivorship is random (invertebrates-hydra).
c. Type III: most individuals die young, with few surviving to reproductive age and beyond (oysters).
population growth
a. Biotic potential: maximum growth rate under ideal conditions (unlimited resources and no restrictions). The
following factors contribute to biotic potential of a species: age at reproductive maturity, clutch size (# offspring produced
at each reproduction), frequency of reproduction, reproductive lifetime, survivorship of offspring to reproductive maturity.
b. Carrying capacity (K): maximum number of individuals of a population that can be sustained by habitat.
c. Limiting factors: density-dependent (limiting effect becomes more intense as population density increasescompetition,
spread of disease, parasites, predation) and density-independent (occur independently of density of
population such as natural disasters or big temp changes).
- Growth rate of population: r = (births – death)/N Change: ∆N/∆t = rN = births - deaths
- Intrinsic rate: of growth is when the reproductive rate (r) is maximum (biotic potential).
d. Exponential growth: occurs whenever reproductive rate (r) is greater than zero (J-shaped).
e. Logistic growth: occurs when limiting factors restrict size of population to the carrying capacity of habitat.
∆N
∆t
= rN (
𝐾−𝑁
𝐾
)
- K is carrying capacity. When population size increase growth rate decreases and reach 0 when population
size reach carrying capacity S-shaped
population cycle
fluctuations in population size in response to varying effects of limiting factors. when population
grows over carrying capacity, it may be limited (lower) than the initial K due to the damage caused to the habitat lower
new carrying capacity K or it may crash to extinction.
Life-history associations
1.K-selected population – members have low reproductive rates and are roughly constant (at K) in size (ex. human population). Have a carrying capacity that
population levels out at. Carrying capacity is a density dependent factor.
2.R – selected population – rapid exponential population growth, numerous offspring, fast maturation, little postnatal care (ex. bacteria). Generally found in rapidly
changing environments affected by density independent factors. Characterized by opportunistic species (e.g. grasses, insects that quickly
invade a habitat, reproduce, then die)
community ecology
concerned with interaction of populations; such as interspecific competition (different species)
- Competitive exclusion principle (Gause’s principle)
: two species compete for exactly the same resources (or occupy the
same niche), one is likely to be more successful (no two species can sustain coexistence if they occupy the same niche).
resource partitioning
: two species occupy same niche but pursue slightly different resources or securing their resources
in different ways, individuals minimize competition and maximize success (multiple species-slightly different niches).
character displacement (niche shift)
as a result of resource partitioning, certain traits allow for more success in
obtaining resources in their partitions reduces competition divergence of features (character displacement) such as
different beak of birds on the same island. The mating calls of 2 species of frogs are different when they occupy the same
island. On separate islands, the mating calls are the same.
realized niche
niche that an organism occupies in absence of competing species is its fundamental niche. When
competitors are present, one/both species may be able to coexist by occupying their realized niches, that part of their
existence where niche overlap is absent (occupy areas of niche that don’t overlap so no competition for resources)
Example: One barnacle species can live on rocks that are exposed to full range of tides (fundamental). In natural
environment, 2nd species of barnacle outcompetes the 1st, but only at lower tide levels where desiccation is minimal. The 1st
species then only survive in its realized niche, the higher tide levels.
predation
: another form of community interaction.
a. True predator: kills and eats another animal.
b. Parasite: spends most of its life living on host, host usually doesn’t die until parasite complete one life cycle.
c. Parasitoid: an insect that lays its eggs on host (insect or spider). After eggs hatch, larvae obtain nourishment by
consuming host’s tissues. Host eventually dies, but not until larvae complete development and begin pupation.
d. Herbivore: animal that eats plants. Granivores are seeds eater (act like predators totally consume organism).
Grazers (animals that eat grasses) and browsers (eat leaves) and eat only part weaken it in process.
symbiosis
– intimate, often permanent association b/w two organisms; may or may not be beneficial; some may be obligatory (one or both organisms cannot
survive w/o the other)
a. Commensalism (+/o) – one benefits, the other is unaffected
Remora and shark – remora gets food shark discards
Barnacle and Whale – barnacle gets wider feeding opportunities
b. Mutualism (+/+) – both organisms benefit
Tick bird and Rhinoceros – bird gets food (ticks) and rhino loses ticks
Lichen (fungus + algae) – algae produces food for itself and fungus via photosynth; fungus provided CO2 and nitrogenous wastes
Nitrogen Fixing Bacteria and Legumes – legumes provides nutrients for bacteria and bacteria fixes nitrogen
Protozoa and Termites – protozoa digests cellulose for termites, termites protect and provide food
Intestinal Bacteria and Humans – bacteria utilized food and provide vitamin K
c. Parasitism (+/-) – benefits at the expense of the host; bacteria and fungi; live with minimum expenditure of energy
Parasites can be ectoparasites (cling to exterior of host) or endoparasites (live within the host)
Virus and Host cell – all viruses are parasites
Disease Bacteria and Animals – diphtheria is parasitic upon man; anthrax on sheep; tuberculosis on cow or man
Disease Fungi and Animals – ringworm is parasitic on man
Worms and Animals – tapeworm and man (less dangerous = more survival; better for parasite not to kill its host)
Saprophytism – protists and fungi that decompose dead organic matter externally and absorb nutrients
Scavengers consume dead animals directly (ex. Vulture, hyena, bacteria of decay)
Intraspecific interactions between members of the same species are influenced by disruptive (competition) and cohesive (reproduction and protection from
predators and weather) forces
coevolution
evolution of one species in response to new adaptation that appear in another species
examples of coevolution
- Secondary compounds: toxic chemicals produced in plants that discourage would-be herbivores (tannins in
oaks/nicotine/ tobacco are toxic)
67 - Camouflage (cryptic coloration): is any color, pattern, shape, or behavior that enables an animal to blend in with its
surroundings. Both prey and predator benefit from camouflage. - Aposematic coloration (warning coloration): conspicuous pattern or coloration of animals that warns predators that they
sting, bite, taste bad, poisonous, or are other wise to be avoided. - Mimicry: occurs when two or more species resemble one another in appearance. There are two kinds:
a. Mullerian mimicry: occurs when several animals, all with some special defense mechanism, share the same
coloration effective with single pattern such [predator only has to learn one pattern is bad instead of lots of variants] as
yellow and black body markings (dangerous) from bees, yellow jackets, and wasps.
b. Batesian mimicry: occurs when animal without any special defense mechanism mimics the coloration of an
animal that does possess a defense.
Coloration, camouflage, mimicry etc are passive defenses. Active defenses are hiding, fleeing, defending but can be costly in energy. - Pollination: of many kinds of flowers occur as result of Coevolution of finely-tuned traits between flowers + pollinators
-red tubular flower coevolves with hummingbird attracted to red provides nectar to hummingbird in exchange for
pollen transfer
ecological succession
1.change in composition of species over time
2.- It describes how one community is replaced by another gradually consisting of different species. As it progresses,
diversity (# of species in community) and total biomass increase. A final successional stage of constant species composition
(climax community), is attained (usually never-random occurs) unchanged until destroyed by catastrophic event
(blowout). Succession has a factor of randomness that makes it hard to predict; resident species can also change a habitat
how can a resident species change a habitat?
- Substrate texture: may change from solid rock, to fertile soil, to sand/others (because rock erodes, plants+animals decomp)
- Soil pH: may decrease due to decomposition of organic matter such as acidic leaves.
- Soil water potential: ability of soil to retain water, changes as soil texture changes.
- Light availability: may change from full sunlight to shady to darkness as trees become established
- Crowding: increases with population growth, may be unsuitable to certain species.
- Pioneer species: plants and animals that are first to colonize a newly exposed habitat (usually opportunistic, r-selected
species); can tolerate harsh conditions. (ex. Lichens and mosses) - As soil, water, light change, r-selected will be replaced by stable K-selected species (live longer, slow succession)
and reach climax where it remains for hundreds of years
primary succession
: occurs on substrates that never previously supported living things (volcanic islands, lava flows).
Essential and dominant characteristic of primary succession is soil building.
secondary succession
: begins in habitats where communities were entirely/partially destroyed by damaging event;
begins on substrate that already bear soil (may contain native seed bank).
- A community stage is identified by a dominant species; Ex: grass in grassland community
- Ecological succession in a Pond
1. Pond: Plants such as algae, pondweed. Animals such as protozoa, insects, fish
2. Shallow water-pond fills in: Reeds, cattails, water lilies
3. Moist land: grass, herbs, shrubs, willow trees. Frogs, snakes
4. Woodland: climax tree – perhaps pine or oak
ecosystems
have trophic levels that categorize plants/animals based on their main energy source.
