Chapter 5: Species Interactions, Ecological Succession, and Population Control

example of tolerance

Shade-tolerant plants can live in shady forests because they do not need as much sunlight as the trees above them do

limiting factors

Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem

Climax community

assumed to be in balance with its environment, occupies an area

Interspecific competition

attempts by members of two or more species to use the same limited resources in an ecosystem

intraspecific competition

competition among members of the same species

No population can grow indefinitely because of limitations on resources and because of...

competition among species for those resources

Population crash

dieback of a population that has used up its supply of resources, exceeding the carrying capacity of its environment

secondary ecological succession

ecological succession in an area in which natural vegetation has been removed or destroyed but the soil or bottom sediment has not been destroyed

primary ecological succession

ecological succession in an area without soil or bottom sediments

5 types of interactions

interspecific competition, predation, parasitism, mutualism, commensalism

facilitation

one set of species makes an area suitable for species with different niche requirements and often less suitable for itself

Predator

organism that captures and feeds on some or all parts of an organism of another species (the prey)

population crash is bound to happen unless...

part of population can switch to new resources or move to an area that has more resources

tolerance

plants in late stages of succession succeed because they are not in direct competition with other plants for key resources

example of mutualism

pollination of flowering plants by honeybees, hummingbirds and butterflies that feed on the nectar of flowers

common limiting factor of land

precipitation

two major types of ecological succession

primary ecological succession and secondary ecological succession

Changes in habitat or other environmental conditions can...

reduce populations of some species while increasing populations of other species

Predator-prey relationship

relationship that has evolved between two organisms, in which one organism has become the prey of another, the latter called the predator.

inhibitation

some species hinder establishment and growth of other species

R-selected species

species with a capacity for a high rate of population growth (r). They tend to have short lifespans and produce many, usually small offspring. These species give them little or no parental care, and as a result, many of the offspring die at an early age

Key factor in determining ultimate population size of species is...

the availability of sustainable habitat with adequate resources

Equilibrium model of succession

what ecologists once meant when they talked about balance of nature

early loss + example

- survivorship is low early in life. - e.g. many r-related species and annual plants

examples of parasitism

- tapeworms - mistletoe plants and blood-sucking lampreys - flies and ticks - certain protozoa (microorganism)

Mutualism

- type of species interaction in which both participating species generally benefit - appear as cooperation between species, but each species is concerned only for its own survival

constant loss + example

- typically has a constant death rate at all ages - e.g. many songbirds

interspecific competition, predation, parasitism, mutualism, and commensalism affect...

...population sizes of species in ecosystems and their use of resources

commensalism

An interaction between organisms of different species in which one type of organism benefits and the other type is neither helped nor harmed to any great degree.

density-independent factors

Any effects they have on population's size are not related to its density

Parasitism

Interaction between species in which one organism, called the parasite, preys on another organism, called the host, by living on or in the host.

Predation

Interaction in which an organism of one species (the predator) captures and feeds on some or all parts of an organism of another species (the prey)

example of facilitation

Lichens and mosses build up on soil on rock in primary succession → herbs and grasses move in → crowd out lichens and mosses

S-Curves + what type of strategists they depict

Mostly seen with K strategists; at the start there are limiting factors but then there is exponential growth and fluctuation around the carrying capacity because of negative feedback mechanisms.

Ecological succession

Natural process in which communities of plant and animal species in a particular area are replaced over time by a series of different and often more complex communities.

example of inhibitation

Needles dropping off pine trees → make soil beneath trees too acidic for most other plants to grow there

Prey

Organism that is killed by an organism of another species (the predator) and serves as its source of food.

Resource partitioning

Process of dividing up resources in an ecosystem so that species with similar needs (overlapping ecological niches) use the same scarce resources at different times, in different ways, or in different places.

J-curves + what type of strategists they depict

R strategists; The curve goes well beyond carrying capacity till it crashes and exponentially decreases. (Boom and bust population growth).

density dependent factors

variables that become more important as population increases

Survivorship curve

Graph showing the number of survivors in different age groups for a particular species

relationship between competition of same resources, niches and time

- Compete for same resources → niches overlap - Greater overlap → more they compete for key sources - Given enough time → populations develop adaptations that enable them to reduce/avoid competition with other species

T/F: Parasites kill their hosts + explain why

- False - Parasite weakens host but rarely kills it, since doing so would eliminate the source of its benefits

constant changes in living systems

- Living systems have complex processes → interact to provide some degree of stability or sustainability - Capacity to withstand external stress and disturbance → maintained by constant change in response to changing environment conditions

Logistic curve

- S-curve - growth that often fluctuates around carrying capacity of its habitat

K-selected species

- Species that tend to reproduce later in life, have few offspring, and have long life spans. Typically offspring of K-selected mammal species develop inside their mothers, are born relatively large, mature slowly, and are cared for and protected by one or both parents - population size tends to be near the carrying capacity (K) of its environment - often vulnerable to extinction

starting point of secondary ecological succession

- area where ecosystem has been disturbed, removed, destroyed → some soil/bottom sediment remains - burned/cut forests, heavily polluted streams, flooded land

starting point of primary ecological succession

- bare rock exposed by retracting glacier - newly cooled lava from volcanic eruption - abandoned highway or parking lot - newly created shallow pond or lake

example of commensalism

- epiphytes (air plants) attract themselves to trunks/branches of trees to gain access to sunlight, water from humid air/rain, and nutrients falling from trees upper leaves and limbs → presence does not harm the tree - birds benefit from nesting trees, generally without harming them

tropical rain forests on inertia and resilience

- high species diversity and high inertia → resistance to low levels of change or damage - Large tract of tropical rain forests cleared or severely damaged → resilience of degraded forest ecosystem → so low, degradation reaches ecological tipping point

late loss + example

- high survivorship to certain age, and then high mortality - e.g. k-selected species

common limiting factor of aquatic systems

- limiting physical factors for population include water temperature, water depth and water clarity (allow for more or less sunlight). - other factors: nutrient availability, acidity, salinity, level of oxygen gas in the water

grasslands on inertia and resilience

- much less diverse than most forests → low inertia and can burn easily - Most plant matter stored in underground roots → ecosystems have high resilience and can recover quickly after fire because root system produce new grasses

how does secondary ecological successions start?

- new vegetation begin to grow, usually within a few weeks - begins with germination of seeds already in soil and seeds imported by wind/droppings of animals

density dependent factors examples

- population density - dense population → parasites and diseases spread more easily → higher death rates - Higher population density → helps sexually reproducing individuals to find mates more easily to produce offspring

why do many opportunist species go through boom-and-bust cycles in their population sizes?

- reproduce and disperse rapidly when conditions are favorable or when disturbance such as fire or clean-cutting forest opens up new habitat for invasion - once established, their population crashes due to unfavorable changes in environmental conditions or invasion by more competitive species

effect of coevolution

2 species interact and prey over long time → genetic changes occur in both species → species become more competitive or reduce competition

coevolution

Evolution in which two or more species interact and exert selective pressures on each other that can lead each species to undergo adaptations.

three factors that affect how and at what rate ecological succession occurs

Facilitation, Inhibition, Tolerance

density-independent factors examples

Flood, fires, landslides, drought and climate change

effects of pioneer species

Successive wave of new organisms change environmental conditions that provide more nutrients, habitats, and favorable environmental conditions for future arrivals

how long do primary ecological successions take and why?

Takes 100s to 1000s of years → need to build up fertile soil/aquatic sediments → provide nutrients needed to establish plant community

Range of tolerance

a range of variations in its physical and chemical environment under which it can survive

resillience

ability of an ecosystem to be restored through secondary ecological succession after a severe disturbance

inertia/persistence

ability of an ecosystem to survive moderate disturbances

examples of r-selected species

algae, bacteria, frogs, most insects, many fish

Pioneer species

first hardy species - often microbes, mosses, and lichens - that begin colonizing a site as the first stage of ecological succession

2 aspects of stability or sustainability in ecosystems

inertia/persistence and resilience

3 generalized types of survivorship curves

late loss, early loss, and constant loss

examples of k-selected species

most large mammals such as elephants, whales and humans, birds of prey, and large and long lived plants such as saguaro cactus, and most tropical rainforest trees

population density

number of organisms in a particular population found in a specific area or volume