Biology
Atmosphere
A layer of gas surrounding the earth, made of 78% nitrogen gas, 21% oxygen gas, 1% argon, water vapour, carbon dioxide, methane and more. Holds temperature at 15 C, and without it global average would be -18. Blocks radiation from the sun
Lithosphere
rocky outer shell of the earth that consists of rocks and minerals, ocean floors, the rest of earth's landscape. Ranges from about 50 - 150 km in thickness.
Hydrosphere
consists of all the water, on, above or below earth's surface. Includes lakes, rivers, ice, groundwater, oceans, clouds.
Biosphere
the locations where life can exist. Majority of species live in the ocean, land, and even underground
abiotic
non living things in an ecosystem
biotic
living parts of an ecosystem
species
a group of organisms that can interbreed to produce fertile offspring. If species are not closely related it is often impossible for the different species to breed, but ones that are closely related produce sterile hybrids
population
a group of organisms of the same species that are living in the same area at the same time. These organisms, if separated geographically or temporally are unlikely to breed, but can. They may start to develop different characteristics if they do not.
community
a group of populations that are living together and interacting in the same area. They are all dependent on interactions with the different species in that community, and they include plants and microbes
ecosystem
a community and its abiotic environment
Autotroph
an organism that synthesizes its organic molecules from simple inorganic substances. They make their own food using photosynthesis. The inorganic nutrient compounds e.g water, carbon dioxide, nitres, phosphorus and oxygen are obtained from the environment. And the rest is taken from the sun and converted into organic compouds (glucose) and stored as complex carbohydrates like lipids, amino acids, etc.
heterotroph
an organism that ingests organic molecules from other organisms. Some unicellular organisms use both methods of nutrition (mixotrophs).Example, venus flytrap: photosynthesizes and eats flies
consumers
feeds on living organisms by ingestion. They cannot make their own food, and rely on other organisms who are recently killed or still alive.
herbivores
feed on producers
omnivores
feed on a combination of producers and consumers
carnivores
feed on other consumers
scavengers
specialized carnivores that only feed on dead or decaying animals
detrivore
a heterotrophic organism that ingests dead organic matter by internal digestion. They eat things like dead leaves, humus, plant parts, feces, and carcasses. E.g earthworms
Saprotroph
a heterotrophic organism that lives on or in dead organic matter, secrets digestive enzymes into it, and absorbs products of digestion. Not consumers as digestion is external. They are called decomposers since they help to break down waste material.
Sustainability of ecosystems
ecosystems can be sustainable, meaning that they maintain a relatively constant set of characteristics over a long period of time. They must have continuous energy availability, nutrient cycling, and recycling of waste.
nutrient cycling
Elements required for growth and metabolism are called nutrients. The supply of nutrients is limited and ecosystems have to constantly recycle the nutrients between organisms. Autotrophs convert nutrients from inorganic form into organic molecules, heterotrophs ingest other organisms to gain organic forms of nutrients, and saprotrophs breakdown organic nutrients to gain energy and release nutrients back into inorganic molecules in the process.
energy flow
all organisms need energy to function. Radiant energy from the sun is the source of almost all this energy. The sun emits invisible radiant energy, including ultraviolet, and visible radiant energy, or light energy. About 70% of this energy is absorbed by the hydrosphere and lithosphere and converted into thermal energy.
Photosythensis
A metabolic pathway. carbon dioxide and along with water is used to produce carbohydrates. Oxygen is released as waste gas. Plants use pigments like chlorophyll to trap light energy which is converted into chemical energy in carbon compounds.
Cellular respiration
a controlled release of energy from organic compounds in cells. Each covalent bond in a glucose, amino acid, etc represents stored chemical energy. When they are broken, energy is released and ATP (adenosine triphosphate) is made. if there is no glucose, other molecules can be substituted. Can be aerobic (w oxygen) or anaerobic (no oxygen). Aerobic only occurs in cells that have mitochondria.
trophic levels
feeding position of an organism in a food chain.
1. producer
2. primary consumer
3. secondary
4. tertiary
5. quaternary
energy loss
typically only 10 - 20% of the chemical energy gets passed on to the organism in the next trophic level. The rest of the energy is used or lost as waste. energy stored in organic molecules can be transferred by cell respiration to ATP. ATP supports the cells metabolism, building and breaking down molecules, growth, and homeostasis. Wasted thermal energy is produced too and it dissipates into the ecosystem and is eventually lost from it.
Pyramids of energy
show the flow of energy between trophic levels. Measured in units of energy per unit area per unit time: kJm^-2y^-1. Transfer of energy is never 100% efficient. Pyramids of energy always get smaller at higher trophic levels due to the loss of energy. Bars should be roughly drawn to scale. E.g secondary consumers should be roughly 1/10 the width of primary consumers. The bottom level will always represent the producers. Biomass is lost between trophic levels. Higher trophic levels are less efficient as more energy is spent on foraging more mobile prey.
the flow of energy through ecosystems step by step
energy enters from sunlight
autotrophs capture sunlight
energy transfer is approximately 10% from one level to another
energy loss due to material not consumed/excreted/etc
energy passes to others
heat energy is lost through cellular respiration
Water
Water (h2o) is made up of two hydrogen atoms covalently bound to an oxygen atom. The end of the oxygen molecule becomes slightly negative, and the hydrogen slightly positive and are said to be polar
key abiotic factors
Terrestrial: light availability, water availability, nutrient availability, and temperature
Aquatic: light availability, nutrient availability, acidity, temperature, salinity
competition
Biotic factor; intraspecific competition: a situation in which members of the same species compete for resources. Interspecific competition: two or more populations compete for resources
predation
biotic factor; one individual feeds on another
disease
pathogens able to pass from host to host in overcrowded populations with greater ease
mutualism
both species in a symbiotic relationship benefit from the relationship or depend on it for survival
commensalism
in a symbiotic relationship where one partner benefits and one is unaffected
parasitism
the parasite benefits from the relationship but the host is harmed by it
biodiversity
is variety of organisms present in an ecosystem. ecosystems with greater biodiversity have greater resilience.
species richness
the number of different species present
species evenness
if a habitat has similar abundance for each species present, the habitat is said to have evenness
resillience
the ability of an ecosystem to remain functional and stable in the presence of outside disturbances.
invasive species
introduced species with growing populations that can have a negative effect on their environment. E.g zebra mussels, European starlings, the cane toad
competitive exclusion principle
two species cannot occupy the same niche in a community, as there will be competition for the same resources. When one species has the slightest advantage or edge over another then the one with the advantage will dominate
impact of invasive species
ecological - they compete with or feed on native species and change ecosystem dynamics
Economic - damage to forests, agriculture, diseases, and pests may destroy livestock and crops
Tourism - species loss and reduced water quality negatively impact wildlife viewing, and waterways can become difficult for boats to pass through
Health - disease-causing organisms, pesticides used to control invasive species cause pollution and health risks
controlling invasive species
chemical control - pesticides are used
mechanical control - physical barriers or removal can be used
biological control - use of an introduction of one organism to control the invasive species
clear cutting
the removal of all or most trees in an area, economical and efficient, takes the shape of large blocks, regeneration can occur naturally or artificially, most common method
shelterwood cutting
mature trees are harvested in a series of two or more cuts, permits regeneration under the shelter of remaining trees, regeneration can be natural or artifical
selective cutting
the forest is managed as an uneven-aged system, foresters periodically come in and harvest selected trees, most costly, but has the least environmental impact
ecological issues in forest management
clear cutting is usually the most profitable method, but it depletes nutrients in the soil and leads to erosion, also only one or two tree species are planted, reducing biodiversity.
biome
large geographical region defined by climate, with a specific set of biotic and abiotic factors
The water cycle
Evaporation – Water is converted
to vapour by the sun and
transferred from the Earth’s
surface to the atmosphere
Transpiration – Water vapour is
released by plants and soil into
the atmosphere
Condensation – Water vapour is
transformed into liquid water
droplets in the air (creating clouds
and fog)
Precipitation – Water vapour in the
atmosphere condenses into liquid
(rain) or solid (snow) and
returns to the Earth
Runoff – The variety of ways water
moves along the ground
Infiltration – The flow of water
from the ground surface into the
soil
Subsurface Flow – The flow of
water underground (will
eventually drain into oceans or return to the surface via springs)
humans and the water cycle
Irrigation removes water from its natural source and often causes leeching (washing of nutrients) and run-off
Generating hydroelectricity requires rivers to be damned which can affect the function of the river both upstream and
downstream. Releasing pollution such as sulfur dioxide and nitrogen dioxide causes a reaction with the water in the air creating acid rain. An increase in pollution may cause the Earth's temperature to rise which also means more evaporation and melting