IB Biology - Ecology

In an closed ecosystem…

energy will be conserved

What is the only truly closed system?

the universe, as Earth is not a closed system so energy is not conserved

Matter is not conserved in…

open systems

Energy is not conserved but…

matter is

What is the source of most energy on Earth?

Sunlight

How is sunlight used in photosynthesis?

Energy in sunlight is used to make glucose in photosynthesis

• Around 1% of the energy from the sun is captured by producers

• The energy is lost as heat - cellular respiration loses some of the energy stored as glucose as heat

• Organisms use most of the energy they consume to produce heat and maintain homeostasis

• The heat given off by organisms goes into the environment

Food Chain

The flow of energy is the process of passing energy from one organism to another through feeding.

Trophic Level

Used to indicate how many organisms the energy level has flowed through.

• 1st trophic level = producers

• 2nd tropic level = primary consumers

• 3rd trophic level = secondary consumers

Pyramid of Energy

Shows how much energy flows from 1 trophic level to another. Uses the unit kilojules per square meter per year (kj x m^-2 x yr^-1)

How much energy is lost from one trophic level to the next?

80%-90% of energy is lost as not all of an organism can be consumed and digested, some organisms are not eaten after they die, and energy is lost through heat,

Gross Production

The total amount of energy trapped in the organic matter produced by plant per area per time in kilojules (kj x m^-2 x yr^-1)

Net production

The gross production minus the energy lost through respiration: has the same unit → (kj x m^-2 x yr^-1)

Food Web

The sum of all the total ways energy can flow through an ecosystem. Organisms can fall into multiple trophic levels, depending on which food web you are looking at.

What are trophic levels specific to?

Food chains, not organisms

Biomass

The dry mass of an organism measured in grams per meter squared per year (g x m^-2 x yr^-1)

Biomass of a trophic level

An estimate of the mass of all the organisms within that level. It is usually expressed in mass (kg) but it may also take into account area/volume and time.

Feed conversion ratio (FCR)

A measure of the efficiency of an animal’s ability to convert feed mass into increased body mass (mass of food eaten/body mass gain). Animals with a higher FCR are theoretically more sustainable for farming

What 4 factors effect population size?

1. Natality - the number of individuals born

2. Mortality - the number of individuals that die

3. Immigration - the number of individuals that arrive from other locations

4. Emigration - The number of individuals that leave for other locations

Population Equation

(Natality +Immigration) - (Mortality + Emigration)

Three Stage of Population Growth

1. The Exponential Phase (growth is exponential) - In ideal conditions like plentiful resources, little competition, favorable abiotic factors, no predation/disease so a population can grow

2. The Transitional Phase (growth slows down) - The ideal conditions are lost to competition, predation, and density dependent limiting factors

3. The Plateau Phase (no population growth) - The population has reached it’s carrying capacity

Carrying Capacity (K)

The maximum number of individuals that a particular habitat can support.

What is carrying capacity determined by?

Limiting factors such as…

• Availability of resources

• Degradation of waste

• Predation

• Disease

• Limiting factors can be top-down (predators)

• Limiting factors can be bottom-up (resource availability)

Studying Population Technique: Capture-Mark-Release-Recapture

A sampling technique that allows you to estimate the number of animals in an ecosystem.

1. You capture a sample of individuals, and mark then in some way

2. They are released

3. You recapture another sample at another time

4. The number of marked individuals is compared to the number of unmarked individuals in the second capture.

Population Size (N)

Size of 1st sample x Size of 2nd sample / number of marked in the 2nd sample

Studying Fish Populations: Studying Catches

For the North Atlantic Ocean, the International council for exploration of the sea samples fish from commercial catches and collects data on types of fish, age, length and breeding conditions. They also survey fisherman about the number of fish released and where they fish.

Studying Fish Populations: Research Vessels

They cast nets into hundreds of locations to study fish populations, and they use sonar to study fish populations

Studying Fish Populations: Calculating the age distribution in fish populations

Knowing the average age of fish populations is important for understanding the health of an ecosystem.

• Ex. Too few older fish = overfishing

• Too few younger fish - lack of spawning

• Fish age can be calculated by studying the otolith bone (ear bone) of a fish

• Mathematical models can also be programmed with data taken from surveys to study fish populations.

Indicator Species

Organisms that are very sensitive to environmental changes. They are used to quickly assess the health of an environment

• ex. Lichens are very sensitive to pollution and can store heavy metals in their tissue

• ex. macroinvertebrates in rivers and streams presence suggest higher water quality

Evenness

The ratio of organisms in the environment. This considers abundance

Richness

The number of different organisms in a particular area. This does not consider abundance

A community is not considered diverse if..

it is dominated by one species

Simpson Diversity Index

A measure of richness and evenness in and environment.

D = N(N -1) / ∑ n(n-1)

• D = diversity index

• n = total number of individuals of each species

• N = total number of organisms in the ecosystem

Management of Conservation Areas: Restoration

• Attempts to return the land to it’s natural state

• Techniques like scrub clearance, cutting/burning, and replanting can be used to restore vegetation

Management of Conservation Areas: Recovery of Threatened Species

• Threatened species are usually helped as we restore their habitat

• This can also help obligate species (a species that is usually not found anywhere but with another species)

Management of Conservation Areas: Removal of Introduced Species

• Most exotic species don’t survive in their new ecosystem without help, however some become invasive species

• Invasive Species: one that thrives in a new environment and outcompetes the local organisms, usually because they have no natural predators. Ex. Lion Fish native to south pacific/indian ocean, invasive to the Caribbean sea

Management of Conservation Areas: Legal Protection against development or pollution

• Nature reserves protected by the government or private organizations can prohibit or limit activities that might harm native organisms (hunting, development, extraction of minerals)

Management of Conservation Areas: Funding and Prioritizing

All method of conservation of ecosystems cost money, so funding these programs is an important step to conserving the land

In Situ Conservation

• Organisms are kept in the environment in which they belong.

• Highly evolved organisms for that specific ecosystem and are vital to playing their niche

In Situ Conservation Aims to…

• Protect the target species

• Remove invasive species

• Defend target species from predators

• Grow the population to a genetically sustainable level

Ex Situ Conservation

• When species are kept in artificial ecosystems

• Used as a last resort when it isn’t safe to keep the species in their natural environment

Ex Situ Conservation: Captive Breeding

• Techniques like artificial insemination, embryo transfer, cryogenics, human-raised young, and pedigrees are used to make sure the programs are ethical

• The goal of these programs is always animal reintroduction to their native habitats

Ex Situ Conservation: Botanical Garden

• Plants are easily kept in captivity and grown artificially

• Over 80,000 plant species are grown in private garden around the world

• Botanical gardens do suffer from underrepresented of wild varieties of crops

Ex Situ Conservation: Seed banks

• Locations where seeds from many different plant species are kept in cold, dark conditions to prevent germination

• Seeds can be preserved in these banks for years

Biogeographical Factors Affecting Species Diversity: Latitude Gradient

This is the effect of climate on species diversity. The further from the equator, the fewer species are present

Biogeographical Factors Affecting Species Diversity: Elevation Gradient

The effect of altitude on species richness. Higher elevation → fewer species

Biogeographical Factors Affecting Species Diversity: Area Effect

The effect of area on species richness. The larger the area in an ecosystem, the more species there will be

Edge Effect

This describes the different ecological conditions seen at the edges of ecosystems. The edges of ecosystems have much less cover, are usually cooler, and have less biodiversity than the center.

All life on earth is…

carbon based - meaning that all organic molecules have carbon present

Carbon is present in both organic and nonorganic forms

Organic: Carbs, Lipids, Proteins, Nucleic Acids, etc.

Inorganic: CO2, Limestome, CO, CH4, etc.

All carbon on earth is..

mostly conserved, so while the form may be changed, it is neither created nor destroyed

The Carbon Cycle

1. Photosynthetic autotrophs use CO2 from the atmosphere and convert it into glucose using energy from the sun.

   • Glucose can be converted into other carbs such as starch, fructose, and galactose

In aquatic systems CO2 is…

dissolved in water. It forms a buffer system with the water.

Limestone

Organisms that form shells (snails, oysters, clams, mussels, coral) use calcium carbonate (CaCO3) to do so.

• When they die, their shells fall to the bottom of the ocean and go through lithification and become limestone, which is then used in buildings.

Carbon Sequestration

The long-term storage of carbon. If it happens naturally it is called biosequestration

Methane (CH4)

A natural gas commonly used for cooking and heating. It undergoes a combustion reaction with oxygen. It is also produced as a waste product in agriculture. It takes millions of years to build up as a natural gas and is being burned at a massive rate, causing an imbalance in the carbon cycle

Peat

Partially decomposed plant material which contains a dry mass of at least 30% organic material. It is waterlogged and highly acidic, but when dried it makes good fossil fuel. Like methane, it is being used much faster than it is being replaced. It eventually become coal when left to condense in a process called lithification

Oil and Gas

Coal, oil, and natural gas are hydrocarbons (chains of carbon molecules attached to hydrogens).

How are oil and natural gas formed?

1. Organic material must be deposited at the bottom of oceans

2. Part of the cells decompose while other don’t, making a wax-like material called kerogen

3. Over hundreds of millions of year, kerogen forms oil and natural gas

4. Crude oil must be refined and separated based on the length of the hydrocarbon before it can be used

Biofuel

The use of biological mass as a fuel

• can be as simple as burning wood for a fire, or as complicated as using oil from fast food restaurants to power a car.

• Biogas chambers use food food waste and animal manure to produce methane for residential use

• Ethanol fermentation chambers are used to create ethanol to supplement gas usage in cars.

• While burning biofuels still releases CO2, it is CO2 that was recently in the atmosphere, as opposed to releasing CO2 from millions of years ago.

Nitrogen Cycling

Driven by bacteria.

1. Nitrogen Fixation - the process of converting atmospheric nitrogen (N2) into ammonia (NH3)

   • Some bacteria form a symbiotic relationship with a host plant and fix nitrogen for it

   • Some bacteria live freely in the soil and fix nitrogen

   • Burning fossil fuels to produce fertilizer can also fix nitrogen

2. Nitrification - The process of turning ammonia (NH3) into nitrite (NO-2). Nitrosomonas is the bacteria responsible for this.

3. Nitrification - Also the process of turning nitrites (NO-2) into nitrates (NO-3). Nitrobacter is the bacteria responsible for this.

4. Active Transport of Nitrates - Nitrates are actively transported by plants into their roots

5. Assimilation - Plants and animals use nitrates to create proteins in their bodies

6. Putrefaction - As the nitrogen is either excreted or the animal dies, it is converted back into atmospheric nitrogen by decomposers.

7. Denitrification - Some bacteria remove nitrates and nitrites and convert them back into atmospheric nitrogen. The bacteria pseudomonas dentrificans is responsible for this process.

Nitrate Concentration in Sewage and Fertilizer

• Raw sewage and commercial fertilizer contain large amounts of nitrate

• These get into streams and lakes and cause major ecological problems as it disrupts the established nitrogen cycles

• They can also cause algae blooms (a spike in the population of algae in a body of water)

• It takes all the oxygen from the water, suffocating anything living there

The Phosphorus Cycle

• Phosphorus is not very common in living systems, so while it is important for life, it isn’t cycled very quickly or easily

• Phosphorus availability is limiting farming practices as it is an important part of fertilizer and we are mining phosphorus faster than it is being replaced

Species

A group of organisms that can be interbed and produce fertile offspring. They also have similar physiological and morphological characteristics, are genetically distinct from other species, and have common phylogeny.

• Have a common gene pool

• The basic unit for classifying organisms

• Made through speciation, which requires reproductive isolation

Hybrids

An organism that has parents of two different species, specifically an interspecific hybrid. Most hybrids are infertile, proving that their parents are from two different species and confirming that the resulting cross is not a new species.

Common hybrid examples

Female Horse + Male Donkey = Mule

Female Horse + Male Zebra = Zorse

Female Tiger + Male Lion = Liger

Autotroph

An organisms capable of making their own organic molecules as a source of food. These are animals that perform photosynthesis or chemosynthesis (aka producers). Ex. Cyanobacteria, algae, grass, trees)

Heterotroph

Organisms that cannot make their own food from organic matter and must consume other organisms, dead or alive, to obtain chemical energy (consumers). Ex. Zooplankton, fish, sheep

The only component of our diet that humans can synthesize is…

Vitamin D - we require sunlight to do so

Detritivore

An organism that eats non-living organic matter

Saprotroph (Decomposers)

An organism that lives on or in non-living organic matter. They secrete digestive-enzymes and absorb the broken-down matter. ex. fungi and bacteria

Communities

A group of populations living and interacting with each other in an area. These only include the biotic/living things in the environment.

Population

All the organisms of the same species that live in a certain area

Limiting Factors

Something that affects the distribution/size of population in an environment.

Abiotic - Non living. Ex. Light, air composition, water availability, temperature, salinity, etc.

Biotic - Living/Were Living. Ex. Intraspecific interactions, interspecific interactions, etc.

Density Dependent Limiting Factors

Density is the number of organisms living in a given area. Affected by the number of organisms in the area. Ex. Competition, parasitism, food availability

Density Independent Limiting Factors

Aren’t affected by the number of organisms in the area. Ex. Light, salinity, climate, pollution

Zone of Tolerance

For every factors, each species has a zone of tolerance which is the range of the factor that organisms can survive in. Has a bell curve made of 5 regions. There is a wide optimal range in the middle where the species is abundant, there are two narrower zones of physiological stress where the species is infrequent but present. There are 2 narrower zones of intolerance where the species is absent.

Keystone Species

A species that is not necessarily abundant but exhibits a strong control over the structure of a community. To determine if a species is keystone, you can perform a removal experiment.

The Paine Experiment and Robert Paine

A species if removed from an ecosystem and the effects are studied. Robert Paine removed a sea star from an intertidal zone. Without the sea stars to eat them, mussels took over the space and outcompeted other algae and invertebrates. The number of species in the area fell from 15-20 to 5.

Habitat

The unique area inhabited by any particular organism

Niche

The role of an organism in it’s ecosystem

Fundamental Niche

The role an organism would play in a perfect ecosystem

Realized Niche

The role an organism plays in the ecosystem it lives in

Competition

When 2 species rely on the same limited resource. Competitive exclusion states that no 2 species can fill the same niche in an ecosystem.

Herbivory

When a primary consumer feeds on a producer

Predation

When a consumer eats another consumer (aka a predator prey relationship)

Parasitism

When an organisms lives on or in a host and depends on that host for part of all of its life cycle. The host will almost always be harmed by the parasite.

Mutualism

When 2 species interact in a way that is beneficial for both organisms

Random Quadrant Sampling

• The process of using quadrats to sample an ecosystem

• A quadrat is a square of predetermined size, usually 1m²

• A quadrat is places down at a random spot in the ecosystem and the species of choice is counted in that quadrat

• This process is repeated until the area is sufficiently studied.

Transect

• A line traces from one environment to another

• The transect can be 10m to more than 50m long. The line can be traced with string or a tape measure

• A quadrat is formed at specific intervals along the transect

• This works well when studying the relationship between distribution of organisms and abiotic factors that change along the transect

Ecosystem

A biological community of interacting organisms and their physical environment

what determines what ecosystem emerges?

Climate (weather, temperature, air pressure, annual precipitation, etc.) A predicted ecosystem is called a climax community

Biome

A division of a biosphere. They are determined by global weather patterns and topography. There are 7 major biomes

1) The Desert

Temperature: Mostly very hot with soil temperatures above 60 C (140 F) in the daytime.

Moisture: Low precipitation (less than 30 cm pear year)

Characteristics of vegetation: Cacti and shrubs with water storage tissues, thick cuticles and other adaptations to reduce water loss

2) Grassland

Temperature: Cold in winter, hot in summer

Moisture: Seasonal drought is common with occasional fires, medium amount of moisture

Characteristics of vegetation: Prairie grasses that hold the soil with their long roots; occasional fire prevents trees and shrubs from invading the grassland.

3) Shrubland

Temperature: Mild temperatures in winter, long, hot summers

Moisture: Rainy winters, dry summers

Characteristics of vegetation: dry, woody shrubs are killed by periodic fires; shrubs store food in fire-resistant roots; they re-grow quickly and reproduce seeds that germinate only after a fire

4) Temperate Deciduous Forest

Temperature: Very hot in the summer, very cold winters

Moisture: High rainfall spread evenly over the year, in winter, water may freeze for a short period of time.

Characteristics of vegetation: Deciduous trees like oak, hickory, and maple dominate forests; in warmer seasons, a wide range of herbaceous plants grow and flower on the forest floor

5) Tropical Rainforest

Temperature: Very warm

Moisture: Very high precipitation of more than 250cm per year

Characteristics of vegetation: High plant diversity; a canopy of trees is the top layer, followed by a layer of shrubs, then a ground layer of herbaceous plants and ferns, large trees have climbing vines; trees have orchids and bromeliads tucked in their branches.

6) Tundra

Temperature: Very cold summers, the upper layer of soil thaws but the lower layer remains frozen (permafrost)

Moisture: Little precipitation

Characteristics of vegetation: Low growing plants like lichen and mosses and a few grasses and shrubs, permafrost prevents roots from growing deeply; continuous daylight in the summer allows some plant growth and reproduction

7) Coniferous Forests (Taigas)

Temperature: Slightly warmer than tundra

Moisture: Small amount of precipitation but wet due to lack of evaporation

Characteristics of vegetation: Cone-bearing trees such as pine, spruce, fir, hemlock

Succession

The change in the biotic and abiotic factors in an ecosystem over time