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ECOLOGY AND BIOLOGICAL CYCLES
Ecological Terms


Ecosystem: all the abiotic and biotic factors in an area/environment surrounding a species



Community: "all the organisms present in an area/habitat/ecosystem"1



Population: "all the individuals of one species in an area"2



Environment: sum of all conditions in the ecosystem outside the organism



Habitat: place within an ecosystem where a particular population is found



Niche: species' function in its habitat
o

Two species occupy different niches when they NOT compete


o

Feeding at different times on different organisms

"Two species NO LONGER occupy the same niche when


one species displaces other species (better adapted)/one species
survives/none survive due to



competition (for environmental resources)/insufficient



food, territory, mates (animals); light, CO2, H2O, mineral ions (plants)"2

Investigating Numbers and Distribution
Investigating Variation


Several samples eliminate chance and anomalies (eg three averaged readings)



Random sampling eliminates bias (favour of one type)
o



Random coordinates achieved by calculator

Any differences must reflect real differences in the population of sampled data

Frame Quadrats


Three measurements can be taken / population size of a particular species occupies in a
quadrat



Assumptions
o
o

Quadrats must be chosen randomly

o


Stationary organisms / must not move
Sample represents whole population

To investigate an area

o
o

Quadrats are chosen at random by using random numbers from a calculator

o


Area is divided into a grid by measuring tapes
Organisms under investigation are counted in each quadrat

To investigate a volume
o

Container of known volume is immersed at random points in the pond

o

Number of tadpoles are counted each time



Limitation: Area being studied is much larger than the small quadrats



POPULATION SIZE = (Sorganisms per quadrat * A of field)/A of quadrat)
o

S = Sum of; A = Area;

Line Transects


Measures distribution of species in a straight line across a habitat



Useful for identifying changes in a habitat



Records all species which touch a tape stretched across a habitat
o

Belt transect records species between two lines

o

Interrupted belt transect records species present in a number of quadrats placed at
fixed points along a line stretched across the habitat



Limitation: one transect may not cross typical areas

Mark-Release-Recapture


Animals are marked and released back into the community (N1)



Second sample is collected
o

Total size of sample (N2) and

o

Number of marked animals (n) are counted



Population size = (N1*N2)/n



Marking must not affect organisms' behaviour / non-toxic marking, survival rate must not be
affected / would make it not more vulnerable to predators



Animals must not die, reproduce, migrate into study area → population size must not change



Marked animals in population must mix

Diversity



Measure of the number of species and their success within an area



Shows stability of an ecosystem



COMPARING DIVERSITY IN TWO HABITATS#






Use large number of traps in each of two habitats
Place traps at random / by random coordinates using a calculator
Keep factor (size/length of time/time of day) constant
Count number of organisms of each type
o N = number of organisms of all species present in the community
o n = number of organisms of each individual species
Calculate index of diversity d = N(N-1) / ∑n(n-1) for both habitats
Takes account of number of individuals (as well as number of species)




Abiotic (non-living) Factors


Climatic factors: seasonal changes in temp, humidity, daylength, rainfall



Physical conditions: pH, soil particles, ions, availability of H2O



Organism must have physiological adaptations to live in abiotic conditions



Lack of inorganic ions (nitrate) often limit plant growth



Plants are primary producers, affecting all populations in a community

Biotic (living) Factors - Interaction Between Organisms


Intraspecific competition / members of the same species compete for resources
o



Space, patch of soil to grow on, nesting site, food,
...
net | Ecosystem | Five Kingdoms

Definition of species (basic unit of classification):


Members of a species are similar (phenotype) to each other but different from other species
o

Similarity of organisms in same species can be



biochemical (haemoglobin structure)



immunological (antibody against an antigen equally effective)



development (similar growth of embryos)




physical (branching pattern of trees)

ecological (occupy identical ecological niche)

(Group of) organisms able to interbreed/reproduce giving fertile offspring
o

Each species is reproductively isolated from every other species

The five-kingdom classification of organisms


Nomenclature: Naming of organisms



Binomial: Biological name of an organism → Genus species



Taxon: Set of organisms within a category / Taxonomy / Study of biological classification



Different levels of taxons: SPECIES, GENUS, FAMILY, ORDER, CLASS, PHYLUM, KINGDOM
o

Most number of species on right

o

Most similar organisms on left



Unicellular: Single cell; Colonial: Groups of cells; Multicellular: Many cells



Autotrophs produce energy from inorganic sources
o

Phototrophs from photosynthesis/sunlight

o


Chemotrophs from simple inorganic (oxidative) processes

Heterotrophs digest and absorb organic molecules

Prokaryotae (prokaryotes)


Cell structure:
o

Prokaryotes, unicellular

o

Prokaryotes lack cytoplasmic organelles found in eukaryotes



Cell wall: murein



Nutrition: autotrophic (photosynthesis, chemosynthesis), aerobic heterotrophs



Divide by binary fission, not by mitosis



≈10μm in size (bacterial cell, filaments of blue-green bacteria)



Mutualistic nitrogen-fixing bacteria live in nodules on the root of legumes / symbiotic

Protoctista (protoctists)


Cell structure: eukaryotes, unicellular and multicellular



Cell wall: (sometimes) polysaccharide



Nutrition: autotrophic, heterotrophic



Placed in this category by exclusion / cannot be placed in any other kingdom
o
o

Protozoa / heterotrophic and ingest food

o


Slime moulds / fungi characteristics
Algae / photosynthesis

≈10μm (amoeba) - 1m (Laminaria / large brown alga)

Fungi


Cell structure: eukaryotes, multicellular and unicellular (yeast)



Cell wall: chitin



Nutrition: heterotrophic / saprotrophic decomposers or parasitic



Genus Penicillium
o

Body of a fungus is composed of thin filaments called hyphae / form a mycelium

o

Secret enzymes / external digestion / absorbs resulting nutrients

o

Erect hyphae that grow upwards from the mycelium carry their reproductive spores

o


Chains of spores on the erect hyphae / coloured mould visible on stored food

Break down organic matter

Plantae (plants)


Cell structure: only multicellular, eukaryotic; large vacuoles



Cell wall: cellulose



Nutrition: autotrophic (photosynthetic)



Growth is restricted to meristems (layers/patches of dividing cells)



Non-motile; adapted to land / strong tissues, leave gas exchange system, waterproofed



Eg mosses, ferns, conifers, angiosperms (flowering plants)

Plant kingdom has two different types of adults in their life cycle


Gametophytes, hidden in plant / sexual reproduction forms multicellular zygotes



Sporophytes, what we call plant / asexual reproduction to form spores that germinate into
gametophytes



Gametophyte (n) → gamete (n) → fertilisation → zygote (2n) → mitosis → sporophyte (2n) →
meiosis → spore (n) → mitosis → gametophyte (n)

Animalia (humans, animals)


Cell structure: eukaryotic, multicellular, no cell wall
o

Develop form a blastocyst / embryo

o

Have nervous and hormonal control systems



No cell wall!



Nutrition: heterotrophic, involving a digestive system



Are motile and grow throughout tissues (no mersitems)

Viruses → acellular → not included in classification system → pathogenic
BiologyGuide

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