APES Chapter 5 - Biodiversity, Species Interactions, and Population Control

Section 5-1 How do Species Interact:

Five types of interactions among species affect the resource use and pop size of soecies.

5 types of interactions between species when they share limited resources.

Interspecific Competition, Predation, Parasitism, Mutualism, Commensalism

Interspecific Competition:

Occurs when two or more species interact to to use the same limited resources such as food, water, light, and space.

Fighting occurs however, most of the time, 1 species has the ability to become more efficient than the other to obtain resources.

Most common interaction between species.

When 2 species use the same resource, their niches overlap. The greater the competition the greater the overlap.

Resource Partitioning:

(resulting from natural selction) Occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, in different places.

Ex. birds(warbles) that live in different parts of the tree.

Predation:

Occurs when a member of one species (predator) feeds directly on all or part of a living organism of another plant or animal species (prey), forming a predator-prey relationship.

Preys defense against predators:

• Escape

• Senses

• Armor

• Camo

• Chem Warfare

• Warning Coloration

• Mimicry (mimicing other species)

• Behavior strategies

• Safety in numbers

Individual and Population effect of predator-prey.

Individual level: predators benefit and the prey does not.

Population-level: predator plays a role in evolution by natural selection.

Symbiosis:

Close, long term association of 2 or more species.

3 different types: Parasitism, Mutualism, commensalism

Parasitism:

(+-) occurs when one organism (the parasite) feeds on another organism (the host), usually by living on or in the host

ex. tapeworms, fleas, ticks

Harmful effects on hosts.

important ecological roles of parasites

Parasites promote biodiversity by keeping hosts populations in check

Mutualism:

(++) is an interaction that benefits both species by providing each with food, shelter, or some other resource.

Ex. pollination of flowering plants from honeybees

Ex. Mycorrhizae - fungi that help plants extract nutrients and water from soil

Ex. gut inhabitant mutualism

Benefits include nutrition and protection

Commensalism:

(+0) Is an interaction that benefits one species but has little, if any, effect on the other.

Ex. birds nesting in trees, or small plants growing in the shade of larger plants.

Ex. epiphytes, forehead mites

Coevolution:

Occurs when two different species interact over a long period of time and changes in the gene pool of one species can lead to changes in the gene pool of the other (ex. bats and moths)

5-2 How do communities and ecosystems respond to changing environemental conditions?

Ecological succession

Ecological Succession

Gradual change in species composition over time in a given area.

Primary Succession

Establishment of communities with different species on nearly lifeless ground (no soil or bottom sediment)

Takes up a lot of time to build up fertile soil or aqua sediment to provide nutrients to plants.

Ex. glacier retreat, landslide, lava, abandoned parking lot

Secondary Succession

Community is disturbed, and the soil/ bottom sediment remains.

Occurs when a series of communities or ecosystems with different species develop in places containing soil or bottom sediment.

Ex. Abandoned farmland, burned/cut forest, polluted stream, flooded land

How does eco succession increase biodiversity?

By increasing species richness and interactions which enhance sustainability by promoting pop control, energy flow, and nutrient cycling which then add to natural capital.

How predictable is succession?

The modern view is that we cannot project the course of succession.

Living systems are sustained through…

Constant Change

3 factors affect how and at what rates succession occurs:

1. Facilitation - 1 set of species makes an area suitable for species with different niche reqs and often less suitable for itself.

2. Inhibition - some species hinder the establishment + growth of other species.

3. Tolerance - plants in the late stages of succession succeed b/c they are not in direct competition with other plants for key resources.

2 aspects of stability or sustainability in living systems:

Living systems contain complex processes that interact to provide some degree of stability. This capacity to withstand external stress and disturbance is maintained by change in response to changing env conditions.

1. One aspect of stability is inertia or persistence which is the ability of. a living system, such as a grassland or a forest, to survive moderate disturbance.

2. A second aspect of stability is resilience which is the ability of a living system to be restored through secondary succession after a more severe disturbance.

5-3 What limits the growth of populations?

No pop can grow indefinetly b/c of limitations on resources and b/c of competition

Population

group of interbreeding individuals of the same species.

most pop live in clumps

Factors affecting pop size (grow, shirnk, or remain stable) :

• pop change equation (pop c=(B+I)-(D+E)

• age structure (stages)

• age and population stability

Immigration

arrivals of individuals outside the pop

Pop Change Equation

Pop change = (births + immigration ) - (deaths + emmigration)

Pop age structure

can have a strong effect on how rapidly a pop grows or declines (pre-reproductive, reproductive, post-reproductive)

Limits on population growth: (5)

• Biotic potential (capacity for growth)

• Intrinsic rate of increase (r) - assumes unlimited resources

• no indefinite population growth

• Environmental resistance = all the factors that limit pop growth

• Carrying Capacity (k) - determined by biotic potential and env resistance

  (review pop growth curve photo in phone Oct 16)

• Population density (diseases can spread quickly)

Species have different reproductive patterns:

R-selected species and K-selected species

R-selected species

species have many, usually small, offspring and give them little to no parental care or protection.

ex. bacteria, insects, algae

Early reproductive age - most offspring die before reproductive age

High population growth rate (r)

Opportunists

Generalist niche

Env impacts on opportunists

low ability to compete

early successional species

population size fluctuates widely above and below carrying capacity

K-selected species

species have few, usually fairly large offspring and invest in parental care and protection

later reproductive age- most offspring survive into reproductive age

adapted to stable climate and env conditions

lower population growth rate

Competitors’

intermediate and variable reproductive patterns

population size is fairly stable and usually close to carrying capacity

specialist niche

high ability to compete

late-successional species

more vulnerable to extinction

ex. humans

Where do most reproductive patters lie

Between the r and k extremes

J-Shaped Curve

Exponential growth

Indv v . time

S-Shaped Curve

Logistic growth - Exponential growth occurs when a pop has essentially unlimited resources however that is then converted to logistical growth in which growth decreases as pop becomes larger and faces env resistance and over time the population stabilizes (Carrying capacity) which results in the s-shaped growth

Can a population grow indefinetly?

No

Carrying Capacity

the max pop of a species that a habitat can sustain indefinitely

When a population size exceeds carrying capacity:

• A species can switch to new resources, move, or die

• Overshoots

• Reproductive time lag

• Population die back or crash

• Human famines (Irish potatoes famine)

• Factors controlling human carrying capacity)

What has increased the carrying capacity for humans?

Tech and other social and cultural changes

3 BIG Ideas (1)

Certain interactions among species affect their use of resources and their population sizes.

3 BIG Ideas (2)

Changes in env conditions cause communities and ecosystems to gradually alter their species compositions and pop sizes (ecological succession)

3 BIG Ideas (3)

There are always limits to pop growth in nature.