Transcript ecosystems and living organisms

Ecosystems and living organisms
Chapter 5
Evolution: populations change
• Evolution: genetic change over time
• Charles Darwin: traits favorable to survival would
be preserved; frequency of favorable traits
increase in subsequent generations
• Adaptation: evolutionary modification that
improves survival and reproductive success
• Natural selection based on observations:
overproduction, variation, limits on population
growth, differential reproductive success
Natural Selection
• Darwin’s finches
exemplified the
variation
associated with
natural selection
• Bottleneck – reduced genetic variation due to
reduced population size. Ex: hunting of
Elephant seals.
• Founder effect – when only a few organisms
colonize an area. Reduced genetic variation;
non-random of original gene pool
Check for understanding
• 4 - I can explain evolution and natural
selection to my peers
• 3 - I understand how variation leads to
varying levels of survival and over time this
leads to evolution.
• 2 - I understand that evolution is genetic
change over time, but I don’t really get how it
happens.
• 1 - I am lost about natural selection and
evolution
Succession: how communities change
over time
• Species in one stage being replaced over time by
others; a constant process; no real climax
community
– Primary succession – occurs where no organisms have
been before; no soil
• Ex: created by volcanic lava, rock revealed by retreating
glacier
• Pioneer community: initial growth, typically lichens which
secrete acid that breaks rock to start forming soil.
– Then mosses and ferns grasses and herbs low shrubs
trees.
– Secondary succession – change in species composition
after a disturbance has destroyed the existing
vegetation; soil is already there.
• Ex: after a fire, abandoned farmland
Secondary Succession of
an abandoned farm field in
North Carolina
Check for understanding
• 4 - I can explain succession (both primary and
secondary) to my peers
• 3 - I understand the difference between
primary and secondary succession.
• 2 - I understand primary and secondary
succession but can’t give examples
• 1 - I am lost about succession
INTERACTIONS
BETWEEN ORGANISMS
Keystone species
• A species that is more important than expected based on
amount to the stability of the ecosystem than others.
– Ex 1: gray wolf – their decline increased herbivore numbers when then
overgrazed. Insects declined because their food (plants) were
declining.
– Ex 2: fig trees in tropical rain forest – animals eat figs when other fruits
are not abundant
– Ex 3: starfish (Pisaster ochracceus) – predator, two mussle species
grow unchecked without them
• Conservation efforts focus on protecting keystone species –
easier to protect just one to balance an entire community.
1. Symbiosis: intimate relationship between at
least 2 species
• A result of coevolution
– Ex: plants and pollinators. Plants have nectar,
pollen, color, scent. Pollinators have hairy bodies,
shape of beak
• Types: mutualism, commensalism, parasitism
• Mutualism – benefits are shared
– Ex: nitrogen –fixing bacteria (Rhizobium) and
legumes (peas/beans); plants get nitrogen and
bacteria get food source.
– Ex: zooxanthellae (microscopic algae) live inside
coral cells and perform photosynthesis.
– Coral gets nutrients (nitrogen, carbon, oxygen) &
calcium carbonate skeletons form around bodies faster
with algae.
– Algae get shelter and nutrients (ammonia waste from
coral and carbon dioxide)
Mutualism
• Ex: Mycorrhizae fungi and plant roots
– Fungus provides better absorption of water and
minerals (like phosphorus)
– Roots provide fungi with food (sugar) produced by
photosynthesis in the plant
Left: root growth
without fungi
Right: root growth
with fungi
• Commensalism – taking without harming
– Ex: epiphytes on trees. Epiphytes gain location for
light, water, nutrients but doesn’t affect tree
• Parasitism – taking at another’s expense
– Rarely kills host
– A factor in the decline of honeybees (in addition
to pesticides and habitat fragmentation)
– Disease/death causing = pathogen
Parasitic
mites in
bee’s
trachea
Other interactions
2. Predation
– Result’s in “arms race”; genetic changes to help capture
prey or avoid predator
– Adaptations:
• Pursuit – better hunting efficiency (like speed)  larger
brains than prey
• Ambush – camouflage or attracting prey (anglerfish)
• Plant defenses – thorns, waxy leaves, toxins (nicotine, opium
poppy)
• Animal defenses – shell, speed, herds, chemicals,
camouflage
3. competition: more than one individual try to
use the same resource
– Intraspecific competition: within population
– Interspecific competition: between species
Check for understanding
• 4 - I can explain at least 4 different ways
organisms interact to my peers
• 3 - I understand many different ways
organisms interact and can give examples of
each.
• 2 - I understand different interactions
between organisms but can’t give examples
• 1 - I am lost about how organisms interact.
Ecological niche
• The role an organism plays in ecosystem
• Includes habitat, what it eats, what eats it,
what organisms it competes with, other
community interactions, how it is affected by
abiotic factors (light, water, temperature)
niche
• Fundamental niche – potential/idealized
• Realized niche – actual niche(less due to
competition)
Factors determining niche
• Limiting factor: any resource –
scarce/unfavorable – restricts ecological niche.
• Competitive exclusion – due to competition,
one species is excluded from a portion of the
niche. (interspecific competition)
– Ex: brown/green anole
– Ex: paramecium – P. aurelia and P. caudatum
(larger)
• Resource partitioning – avoid/reduce resource
competition; favored by natural selection; no
two species have exact same niche
Interspecific Competition
Check for understanding
• 4 - I can explain to the class the relationship
between interspecific competition, competitive
exclusion, and resource partitioning.
• 3 - I understand interspecific competition,
competitive exclusion, and resource partitioning.
• 2 - I understand the definitions, but need some
more practice.
• 1 - I am lost about interspecific competition,
competitive exclusion, and resource partitioning
Species richness
• # of species in community; increases community
stability; affected by:
– Abundance of niches
– Ecotone: zone between communities, increased species
richness due to increased quantity of niches (edge effect)
– Geographical isolation – decreases richness (smaller area
decreases available niches); ex: islands, mountaintops; the
more isolated and smaller in size decreases richness.
– Dominance of one species reduces richness: takes
resources/outcompetes other species
– Environmental stress of habitat reduces richness (polluted
stream)
Ecosystem services
• what ecosystems do for other organisms,
including humans
• Greater species richness = better ecosystem
services
• Ex: provide habitat, forests provide wood,
purify air/water and absorb CO2, grasslands
provide humans with livestock, rivers provide
recreation and methods of transportation
Check for understanding
• 4 - I can explain to the class how ecosystem
services are related to species richness.
• 3 - I understand factors that influence species
richness and can define ecosystem services.
• 2 - I either understand only species richness
or ecosystem services, but not both fully.
• 1 - I am lost about ecosystem services and
species richness