Biology Unit 1

Ecosystems and Population Change

Ecology

Ecology is the study of how organisms and living things interact with each other

Biotic Factors

• Living factors that affect organisms

  • Examples: bacteria, algae, plants, animals, availability of producers (food)

Abiotic Factors

• Non-living factors that affect organisms

  • Examples: sunlight, water/rocks/soil (physical environment), temperature, pH, climate

Population

All members of the same species living within the same ecosystem/habitat (a singular species in the ecosystem)

Community

A collection of all populations in the same ecosystem/habitat (all biotic life)

Ecosystem

All biotic and abiotic factors interacting with each other and their physical environment (abiotic and biotic things in an invironment)

Ecological Niche

An organism’s role within its ecosystem

Components of an ecological niche

Components of an ecological niche include everything an organism does ot survive and reproduce

• Place in food web (e.g. producer, consumer→primary/secondary/tertiary)

• Habitat

• Breeding area

• Most active time of day (e.g. nocturnal)

Competition drives ______

Adaptation

Resource Partitioning

Division of limiting resources amongst competitors by:

• Using a different resource (e.g. food)

• Using same resource but in a different area

• Using different parts of the same resource

• Using same resource at different times of the day

Invasive species

• Invasive species are non native species that threaten the balance of native ecosystem

• Invasive species are usually introduced into an ecosystem by humans

Invasive species are usually introduced into an ecosystem by humans

• If a prey species, it has no natural predators

• If a predator species, native species have no adaptaions against it

• May be better adapted to the environment

• May reproduce very quickly

• Example: The Can Toad:

  • Native to Central and Southern America, Cane Toads were introduced to Caribbean Islands and Australia as a method of pest control (natural beetle predator)

  • Has poison glands, tadpoles are extremely toxic if ingested and its skin can kill many animals. Toxin has hallucinogenic properties but also causes heart complications, seizures and even death in humans.

  • Eats like crazy and eats many native animals without any threat

Biosphere

The biosphere refers to all the ecosystem’s of the earth.

Ecosystems vary based on:

biotic factors (living) and abiotic (nonliving: climate, local geography, etc.)

Biome

A biome is a large geographical area with a specific regional temperature and precipitation and organisms that are adapted for those conditions.

Ecological hierarchy

Organism→ species→ population→ community→ ecosystem→ biome→ biosphere

Terrestrial Biomes

1. Forests

2. Tundra

3. Deserts

4. Grasslands

Types of forests

1. Tropical (rainforest, jungle)

2. Temperate

   1. Deciduous (loose leaves→aspen, oak)

   2. Coniferous (evergreen, pine trees)

3. Taiga/Boreal forest (cold, evergreen trees)

Types of grasslands

1. Savannas

2. Prairies

3. Steppes

The four major terrestrial biomes in Canada

1. Tundra

2. Boreal forest/taiga

3. Deciduous forest

4. Grasslands

Factors affecting terrestrial biomes

• Availability of water

• Availability of sunlight

• Temperature

• Soil conditions

Abiotic and biotic factors in the taiga/boreal forest

Abiotic:

• Largest terrestrial biome

• Northern latitudes

• Changing seasons (cold and warm months)

• Short, wet summers

• Long, cold sinters

• Dense canopy (top of treeline)→low sunlight filters to the ground

Biotic

• Mainly evergreen trees

• Black/grizzly bears

• Moose/deer/elk, etc.

• Spruce, pine, shrub

• Some ferns, mosses, lichen

Abiotic and biotic factors in the grasslands

Abiotic:

• Prairies (central, southern Alberta)

• Rich, fertile soil; “bread basket”

• More sunlight, higher temperature compared to taiga

• Found in temperate zones

Biotic

• Tall/mid height grass (prairies)

• Rapidly flowering plants

• Coyotes, golden eagles

• Snakes

• Rodents (ground squirrel, deer mouse)

Abiotic and biotic factors in the deciduous forest

Abiotic:

• More sunlight, higher temperature

• Rich, fertile soil

• Well defined seasons

• Year round precipitation

• Mid latitude regions

• Less dense canopies→sunlight reaches the ground

Biotic

• Aspen, oak, birch, poplar trees (deciduous trees)

• Lots of shrubs

• Deer, elk, moose, etc.

• Woodpeckers

Abiotic and biotic factors in the tundra

Abiotic:

• Very low temperatures

• Very little precipitation

• Nutrient poor soil

• Minimal sunlight in winter

• Very short growing season

• Frozen permafrost layer that exists year-round

• Not found in Alberta

• Alberta has muskeg→grassy bog with permafrost

Biotic

• Short, low-lying herbs and shrubs adapted to harsh climates

• Arctic fox, polar bears

• Ptarmigans

Characteristics of aquatic biomes:

• Photosynthetic organisms (aquatic) account for more that 50% of global photosynthesis

• Consume vast amounts of CO2 (regulates climate)

• Regulate weather patterns

• Provide a constant supply of freshwater (evaporation)

Freshwater ecosystems

• Contains ~500ppm of salt

• Covers ~3% of Earth’s surface

• Most freshwater on Earth is in the form of ice and snow (~70%)

• Streams, rivers, ponds, lakes, wetlands

• Streams and rivers are running water

• Lakes and ponds are standing water

• Ponds: light reaches the bottom

• Lakes: light does not reach the bottom in most of the lake→regions where photosynthesis cannot occur

*Pollutants can accumulate in a lake and nutrient buildup in lakes can cause eutrophication

Marine Ecosystems

• Contains 35,000ppm of salt

• Defined by proximity to shore and depth of water

• Proximity to shore

  • Intertidal zone: Shoreline (where land meets sea)

  • Pelagic zone: Open ocean of any depth

  • Benthic zone: Sea floor itself

• Depth of water (amount of light penetration):

  • Photic zone: Light can penetrate up to 200m→region where photosynthesis occurs

  • Aphotic zone: At depths of more than 200m, little to no light penetration so there is no photosynthesis (comprises most of the ocean)

These properties vary with the depth of a lake:

• Amount of light penetration

• Temperature of water

• Oxygen levels available

Three main zones of a lake:

1. Littoral zone

2. Limnetic zone

3. Profundal zone

Littoral zone

• Area extending from shore to where plants no longer grow on the lake bottom

Biotic factors:

• Aquatic plants (bulrushes, water lilies)

• Insects, crustaceans, frogs, other amphibians→attracts larger animals which feed on them (birds→ducks)

Limnetic zone

• Area where there is open water and enough light for photosynthesis to occur

Biotic factors:

• Plankton (photosynthetic type of algae)

Profundal zone

• Region beneath the limnetic zone where there isn’t enough light for photosynthesis

Biotic factors

• Only source of nutrients is detritus from decaying organisms that fall to the bottom→can support some detritus feeders like bacteria and fungi and some arthropods

Limit of effective light penetration

200 meters

Ecotones

• Ecotones are transitional areas between different species

• They contain species from both bordering ecosystems, so they often contain greater biodiversity

Biodiversity

Variety/number of different species

Artificial ecosystems

Artificial ecosystems are planned ecosystems managed by humans.

• Examples: Wildlife parks, zoos, city parks, gardens, artificial ponds or lakes

• Change is limited due to human interference → we don’t see significant changes in biodiversity (e.g. weeding out a garden)

Natural ecosystems

Natural ecosystems are naturally occurring (unplanned) ecosystems

• Examples: natural biome (“the wilderness”, rainforest, boreal forest, etc. )

• Changes gradually over time (evolution/adaptation) as organisms best suited to the environment flourish (survival of the fittest)

Changes that result due to human interference

• Introduction of invasive species can cause depletion/extinction of native species → Bad (what we see most of the time)

• Conservation efforts (e.g. protected wildlife areas) → Good

Limiting factors

Limiting factors are abiotic and biotic factors that limit the distribution (spread) and size (growth) of the population over time.

What are the four different layers of soil

1. Litter

2. Topsoil

3. Subsoil

4. Bedrock

Litter

• Partially decomposed plant materials (e.g leaves)

• is the topmost layer of soil

Topsoil

• Small rocks (i.e. minerals) mixed with humus

• Is the second layer of soil

Humus

• Decaying organic matter

• Is part of topsoil and some parts of the subsoil

Subsoil

• Larger rocks and less/no humus

• Is the third layer of soil

Bedrock

• Rock layer at the end of soil

• Is the bottom layer of soil

• In many cases, this is impervious (doesn’t allow water to pass through)

What determines the availability of water

Depends on type of precipitation and type of soil → groundwater collects in rocks/soils below Earth’s surface by seeping through porous rock

What changes the temperature

Varies seasonally and based on geograpic region/climate

What determines the level of sunlight

At the equator, it doesn’t vary much but at the poles, it varies seasonally. Taller trees form a canopy that blocks sunlight from reaching the understory.

Canopy

The tops of the tree line → a thicker canopy will block more sunlight from reaching the understory than a thinner one.

Understory

The very bottom of a forest and is usually comprised of bushes and small plants.

Chemical environment

The dissolved chemicals (types and concentrations) in the aquatic ecosystem

Examples:

• pH environment (presence of acids)

• Phosphates and nitrates(nutrients that can come from fertilizers)

• Dissolved oxygen (the greater the temperature, the less the oxygen dissolved)

• Pollutants

• Salt (marine vs. freshwater ecosystems)

Temperature as a limiting factor in aquatic ecosystems

Temperature is affected by depth/availability of sunlight

• The deeper the water, the less the sunlight, the lower the temperature

• Hydrothermal vents allow life to thrive at the most extreme depths in warm environments

Sunlight as a limiting factor in aquatic ecosystems

Sunlight caries with depth (aphotic vs. phtoic zones)

Water pressure as a limiting factor in aquatic ecosystems

Water pressure increases as depth increases → specialized adaptations at extreme depths

Water density as a limiting factor in aquatic ecosystems

Water density increases as water temperature decreases until it reaches ~4°C when water density begins to decrease as water temperature increases (why ice floats)

Lake turnover

Seasonal variations cause changes in abiotic conditions which affect freshwater lakes.

What happens to lakes in winter?

The lakes are covered with snow and ice (less dense than water) which floats causing the water beneath to be insulated and stay at a steady, positive temperature.

Thermal stratification

Lower levels of a lake are arranged in layers

The three layers in a lake

1. Epilimnion

2. Hypolimnion

3. Thermocline

Epilimnion

The upper level of a lake: Warms up during the summer, cool down during the winter

Hypolimnion

The lower level of the lake: Is the densest level and remains at a constant temperature of roughly 4°C year round

Thermocline

Is the zone between epilimnion and hypolimnion → experiences rapid temperature changes (depends on the season)

Lakes in winter

• The layer of ice on the surface insulates the layers below; prevents atmospheric oxygen from dissolving

• The liquid water in the lake has a depleting oxygen supply because the animals in the lake are using the oxygen up

Lakes in spring

• This is a turnover period

• The ice thaws/melts so oxygen can dissolve in the water

• Increased temperature means the water becomes more dense until 4°C → upper layer starts to sink and mix in with the lower layer → this adds oxygen to the lower layer

Lakes in the summer

• During the summer, the epilimnion warms up and you get density changes and some cycling in the epilimnion only

Lakes in autumn/fall

• This is a turnover period

• Temperatures drop: density increases until 4°C: denser water sinks and mixes with the lower layers

Biotic potential

The maximum number of viable offspring that individuals within a species can have (with unlimited resources)

4 Factors that determine biotic potential

1. Birth Potential

2. Survival Capacity

3. Breeding Frequency

4. Reproductive Lifespan

Birth potential

The number of offspring per birth

Survival Capacity

Th number of offspring that survive to reproductive age.

Breeding frequency

The number of times that a species reproduces per year.

Reproductive lifespan

The age of sexual maturity + the number of years the individual can reproduce.

Limiting Factors

• Factors in the environment that prevent populations from reaching their biotic potential

• Think of limiting factors as resources that are in short supply or are directly harmful agents

Abiotic Limiting Factors

• Light: Affects photosynthesis → affects producers → affects consumers

• Temperature: Ideal temperature ranges for survival and reproduction (e.g. eggs hatching)

• Chemical environment: Favourable chemical environment (e.g. dissolved oxygen, pH) and unfavourable chemical environment (e.g. pollutants, excess nutrients)

Biotic limiting factors

• Food availability: Indicated by number and diversity of producers

• Predator effectiveness: Many vs. few, Weak vs. strong

• Parasites: organisms that weaken/kill hosts to survive

• Ability to compete for resources: Mating strategies (e.g. antlers in a male deer), population density (increased resource competition)

Carrying Capacity

• The maximum number of individuals of a species that an ecosystem can support.

• The carrying capacity is determined by interactions of biotic and abiotic limiting factors→populations commonly fluctuate based on limiting factors

Law of the minimum

The nutrient in the least supply is the one that limits growth.

Law of tolerance

Specific range of an abiotic factor that organisms can survive in.

Optimum range

The highest rates of survival (largest population size)

Population density

The number of indiviudals within a given area.

Density independent factors

• A factor that affects members of a population regardless of population density

• Ex: Earthquakes ,volcano eruption, asteroid impact, natural disasters, climate change, flood, pollution/toxins, pesticides

Density dependent factors

• A factor that affects members of a population because of the population density

• Ex: Infectious disease, resource competition for mates or resources, water availability, food availability, predation, invasive species, competition for mates, habitat availability

Lake and pond succession

Progressive change in the composition of living organisms (plants, animals, etc.) over time.

lakes refill by:

• Precipitation

• Glacier melt

• Surface runoff

• Inflow from groundwater

Eutrophic lakes

• Have high nutrient levels

• Clear, blu water

• High oxygen levels

• Cold water

• Deep water

• Sediment is settled at teh bottom of the lake

Oligotrophic lakes

• Have low nutrient levels

• Shallow, murky water

• Low oxygen levels

• Sediment buildup

• Lots of living organisms

Eutrophication

• Oligotrophic lakes become eutrophic over time

• Dead animals/plants and debris from wind and erosion causes the shallow ends of the lake to change/age→These are signs of eutrophication

Progression of eutrophication

1. Oligotrophic lake → low water temperature, high oxygen content, high depth

2. Lake increases in temperature, decreases in oxygen content, and decreases in depth and increases in plant/animal biodiversity

3. Eutrophic lake: high water temperature, low oxygen content, low depth, high plant/animal biodiversity

4. Lake dries up

Climatographs

• A summary of average temperature and average precipitation of each month in a year in a locale

• Can be used to determine the biome you are studying

• Vertical right axis: temperature (line graph)

• Vertical left axis: precipitation (bar chart)

BOD

Biological oxygen demand:

• The amount of dissolved oxygen that is needed by decomposers (mainly bacteria) to break down organic matter in a water sample→rate of oxygen consumption

• Can indicate the available organic matter in a sample

• Increased number of organisms = increased BOD

• Cold, less productive lakes with less organisms have a lower BOD than a more productive lake→more dissolved oxygen

• As the number of organisms increases, the BOD increases

• If the BOD surpasses the dissolved oxygen available, eutrophication occurs and organisms begin to die off

Eutrophication (algae blooms)

• Occurs when excess nutrients enter lakes causing excess growth of algae and other aquatic plants

• Nutrients come from nitrates/phosphates from fertilizer runoff and sewage runoff (poop)

• Plants/algae die off and decomposers break them down→uses up oxygen

• Oxygen continues to be depleted, causing more organisms to die off

Three kinds of deforestation

1. Slash and burn

2. Clear cutting

3. Selective cutting

Slash and burn

Bulldoze trees and burn them→used when lands needs to be cleared quickly

Clear cutting

Removal of all trees in a specific area for use in timber/lumber and pulp for paper

Selective cutting

Removal of certain trees in an area

Prescribed burns

Set intentional fires to maintain the ecosystem integrity and to prevent future wildfires.