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5. Ecology

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Ruru (Juan Ru) Hoong

on 23 June 2014

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Transcript of 5. Ecology

5. Ecology
5.2 The Greenhouse effect
5.3 Populations
5.4 Evolution
5.5 Classification
5.1.1 Define species,
habitat, population, community, ecosystem, and ecology.
: a group of organisms that can interbreed and produce fertile offspring.
: the environment in which a species normally lives or the location of a living organism.
: a group organisms in the same species that lives in the same area at the same time.
: a group of populations that live and interact with each other in the same area.
: A community and its abiotic environment.
: a study of the relationships between living organisms and their abiotic environment.
5.1.2 Distinguish between heterotrophs and autotrophs
are organisms that synthesize their organic molecules from simple inorganic substances (eg. via photosynthesis).
are organisms that obtain their food from organic molecules of other organisms.
5.1.4 Describe what is meant by a food chain, giving 3 examples, each with 3 linkages.
Food chain
: a diagram showing the direction of energy flow from one organism to another, illustrating feeding relationships.
5.1.9 State that light is the initial energy source for almost all communities.
The Sun is the source of energy.
5.1.11 State that energy
transformations are never 100% efficient
Only 10% efficient.
5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled.
Energy is not recycled
Enters/ supplied to ecosystems
Flows through trophic levels and passed to decomposers; energy loss as well
Metabolism: heat energy
Nutrients are constantly recycled
Limited supply of nutrients
Nitrogen absorbed as nitrates; amino acid; animal protein; excretion; urea back to nitrate
Cycle: sapotrophic bacteria and fungi break down nutrients & are essential to recycling
5.1 Communities and Ecosystems
5.1.3 Distinguish between consumers, sapotrophs, and detritivores.
: organisms that ingest other organic matter that is living or recently killed.
: organisms that live in or on non-living organic matter, secreting enzymes onto it and absorbing the products of digestion, breaking down dead/ decaying material.
: an organism that ingests non-living organic matter
algae - mayfly larvae - juvenile trout - kingfisher
phytoplankton - krill - chinstrap penguin - seal - great white shark
grass - grasshopper - meerkat - eagle
5.1.5 Describe what is meant by a food web.
A diagram that shows all the feeding relationships in a community with arrows that show the direction of energy flow.
5.1.6 Define trophic level
Trophic level: the position of an organism in a food chain (feeding level).
5.1.7 Deduce the trophic level of organisms in food chain and food web.
Producers: plants and other photosynthetic organisms.
Primary consumers/ herbivores: species that eat producers.
Secondary consumers:
feed on primary consumers
Tertiary consumers:
feed on secondary consumers

* Carnivores/ omnivores
5.1.10 Explain the energy flow in a food chain.
5.1.12 Explain reasons for the shape of pyramids of energy.
Producers receive energy from light energy (Sun) by photosynthesis
Primary, secondary and tertiary consumers consume one after another
Energy from organic matter flows
However energy is always lost (about 90%)
Not all of the organism is consumed/ ingested as food source
Not all ingested food is assimilated
Egested in faeces
Tissue loss and death
Metabolism: cell respiration uses up energy
Maintain homeostasis
Movement: expend energy
Lost to environment as heat
Energy in faeces and dead/decaying matter passed to decomposers
Digestion and breaking down; recycles nutrients
Lose energy through heat as respiration
Pyramids of energy are diagrams representing transfer of energy between trophic levels.
Width of each layer proportional to amount of energy it represents
Smaller increase as only 10% transferred to each level due to energy loss
Energy link in the chain suffers losses
Eventually insufficient energy to support further trophic levels; around 3 - 4, not more than 6
light energy - chemical energy - heat energy
5.2.3 Explain the relationships between the rise in concentration of atmospheric CO2, methane and oxides of nitrogen and the greenhouse effect.
Carbon dioxide:
rotting/ burnt vegetation/ deforestation
combustion of fossil fuels
5.2.1 Draw and label a diagram of the carbon cycle to show the processes involved.
Cows: cattle ranching or farming
Paddy fields
Nitrogen oxides:
Motor vehicle engines/ exhaust
Aerosols/ foams
The earth's mean average temperature is regulated by a steady equilibrium which exists between the energy reaching the Earth from the Sun & energy reflected back
Incoming shortwave ultraviolet visible radiation
Some absorbed by atmosphere, some reflected back as longer wave infrared radiation
Greenhouse gases absorb this infrared radiation and re reflect it towards Earth
Greenhouse effect: increase in average mean temperatures
Rise in global warming due to rising human population
Enhance the effect
Increase CO2 concentration & global temperature
Changing climate
Extinction of species
Glaciers melting/ increasing seal level/ flooding
Increased photosynthesis
5.2.4 Outline the precautionary principle.

The precautionary principle suggests that if the effect of a change (human-induced) is likely to be very harmful, action should be taken to prevent it, even if there is not sufficient evidence that it will cause harm
Those concerned about the change will not have to prove that it will do harm - rather, those responsible have to prove that it will do no harm

Moral and political principle to protect public
and environment
5.2.5 Evaluate the precautionary principle as a justification for strong action in response to the threats posed by the enhanced greenhouse effect.
Global warming has consequences for the entire human race and an international solution is needed
Better to invest in a sustainable future rather than cause harm to future generations
Strong evidence and correlation
If some invest to be environmentally friendly, polluting companies have an cost advantage
Misuse by pressure groups
Prevent business
5.2.6 Outline the consequences of temperature increase or Arctic ecosystems
Permafrost melts, increasing rate of decomposition of detritus
Migrations of species disrupts balance of ecosystem and food chains
Temperature change in sea so sensitive marine life face extinction
Rise in pests and diseases
Exposure of cryoconite, even blacker more melting
Loss of habitats
Melting ice caps and glaciers lead to rising sea level/ flooding
Freshwater changes salinity/ currents; change of distribution of nutrients
5.3.1 Outline how population size is affected by natality, immigration, mortality, and emigration.
: increases population size as offspring are added to population
: decreases population size as individuals die
: increases population size as species arrive from elsewhere
: decreases population size as individuals move to new habitats
5.3.2 Draw and label a graph showing a sigmoid population growth curve
5.3.3 Explain the reasons for the different phases.
Rapid increase in population
Natality > Mortality
Abundance of food and resources
Few predators/ diseases
Little accumulation of waste
Transitional phase
Natality decreases and mortality increases
Decrease in the abundance of resources due to increase in population, more competition
Increase in number of predators
Increase in diseases and waste build up
Natality still > mortality, just smaller population increase
Plateau phase
Natality = mortality; population constant
Reached carrying capacity of environment
Limiting factors to population
5.3.4 State 3 factors that limit population increase
1. Accumulation of waste (toxic waste build-up)
2. Diseases
3. Predation
4. Lack of food/ resources/ water
5. Lack of shelter
5.4.3 State that populations tend to produce more offspring than the environment can support.
5.4.6 Explain how sexual reproduction promotes variation in a species.
During meiosis, genetically different haploid gametes are created
Prophase I crossing over
Metaphase I random assortment
Fertilization brings together different alleles, promoting variation
Enormous source of genetic diversity and wider variation in addition to mutation
5.4.7 Explain how natural selection leads to evolution.
Variation in organisms/ individuals in a population
Some have characteristics that are advantageous to survival in the surroundings
Adapted to environment, better eyesight, etc.
Out compete others, less adapted die, more adapted survive and pass on advantageous features to offspring (competition due to lack of food, etc.)
Natural selection: occurs as fittest survive to reproduce
5.4.8 Explain two examples of evolution in response to environmental change.
Peppered moth
Light-speckled gray - camouflage against the trees
Black formed appeared in mid- 19th century in Britain
Industrial revolution and resulting pollution killed lichens and bark became black
Due to a single gene - dominant allele gray, recessive black
Black better camouflaged, survived & bred and changed to black
5.5.2 List 7 levels in the
hierarchy of taxa:

Corn Plant
Zea mays
5.5.1 Outline the binomial system of nomenclature
Naming system introduced by 18th Century Swedish naturalist Carolus Linnaeus
Classification of living organisms: organizing into groups to show similarities and differences
Taxonomy is the science of identifying, naming and grouping organisms
First part genus, second part species
Binomial: two names
5.4.1 Define evolution.
Evolution is the cumulative change in the heritable characteristics of a population.
5.4.2 Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals & homologous structures.
Fossil Record
Selective Breeding of Domestic Animals
Homologous Structures
Collection of preserved remains of dead organisms (eg. imprints/ bones)
Although fossilization is rare and the likelihood of finding one is rare, we can deduce age, haitat, diet, features & characteristics of species
Show a gradual change over time
Artificial selection is a good model of natural selection
Advantageous characteristics are identified and interbred, cumulative change brought about
Although different (and not always selecting survival of the fittest), it shows that a species can change over time
Similar anatomical/ structural features in shape/function in different organisms
Imply a common ancestor
Eg. Pentadactyl limb in vertebrates are adapted to different locomotive functions
Bat's wing and human hand
Adapted to different niche: cumulative change
5.4.4 Explain that the consequence of potential over production is a struggle for survival.
Less resources available to support entire population
Resources become scarce and there is competition for survival
Weaker individuals in population will lose out on vital resources: increase in mortality.
5.4.5 State that the members of a species show variation.
Antibiotic resistance
Drugs kill and inhibit antibiotic cell walls
Due to variation, a few resistant bacteria aren't killed
More resources, asexual reproduction, resistant offspring
Out compete normal susceptible strain and replace them
Plasmids can be exchanged with other bacteria with resistant genetic material
Have to keep developing new antibiotics
A classification system for organisms is needed to:

Allow simple and precise communication
Provide quick and accurate description
Assist in identification of unknown organims
Show trends
Show evolution: simple - complex
5.5.3 Distinguish between the following phyla of plants, using simple external recognition features.
Small and grow in damp places as they have no vascular system to carry water
No roots but just filamentous outgrowths called chizoids
Reproduce by spores, contained on capsules on small stalks held above plant
No cuticle an absorb water across surface
Liverworts have a flattened structure: thallus; mosses: leaves
Flowering plants
Have flowers that produce pollen
Seeds in the fruit/ nut
Produce pollen rather than spores
Produce seeds, found in cones
Needle-like leaves
Some can grow to 15m tall due to support from woody tissue
Have roots, stems, leaves, and internal structure
Some have fibrous roots, other underground stem called rhizome
Reproduces by spores (in ferns, clusters on undersides of leaves)
5.5.4 Distinguish
between phyla of animals
No clear symmetry
Pores through body to pump out water and filter food
No mouth or anus
No nervous or muscular tissue
Aquatic and attached to surface
Bilaterally symmetric
Mouth but no anus
Three layers of cells and has a body cavity
Bilaterally symmetrical
Mouth and anus
Bristles called chaetae
Muscular foot and mantle
Shell may be present (calcium carbonate)
Segmentation not visible
Mouth and anus
Radially symmetric
Stinging cells
Mouth but no anus
Cells organized in two body layers
Largest phylum
Exoskeleton made of chitin
Bilaterally symmetric
Jointed appendages
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