IB Biology - Ecology

Biodiversity

the variety of life in all its forms, levels + combinations

Ecosystem diversity

variety of habitat types or ecological niches within a given area

Genetic diversity

Variety of genes + characteristics that are present within a population of a species

Species diversity

range of different species that are found within a particular habitat or ecosystem → measured in terms of species richness (number of different species) and species evenness (number of individuals in a species)

Comparisons no. of species on Earth VS past levels of biodiversity

Biodiversity is constantly changing due to:

• speciation → new species evolves, increasing biodiversity

• extinction → decreases biodiversity

Fossils

Evidence from fossils suggests that there are currently more species alive than at any point in the past

How to classify species

1. Lumpers

2. Splitters

Lumping

Lumpers group similar organisms together through shared similarities → fewer species recognised

Splitting

Splitters separate organisms based on differences → more species recognised

Anthropogenic species extinction

the permanent loss of a species caused directly or indirectly by human activities

North Island Giant Moa

The giant moa was a flightless bird → before the arrival of humans, the moa’s only predator was the massive Haast’s eagle → after polynesian settlers came, the giant moa was quickly driven to extinction by overhunting + habitat destruction

Caribbean Monk Seal

The Caribbean monk seal lived in the oceans around the gulf of Mexica + the Caribbean → their docile nature made them easy prey to humans, who hunted them for their oil + blubber → overfishing of their food source led to starvation

Tasmanian Tiger

The Tasmanian tiger was native to the Australian mainland and the island of Tasmania → died out on the mainland due to competition with dingoes → the arrival of European settlers, the Tasmanian tiger was intensively hunted

Examples of ecosystem loss

1. Mixed dipterocarp forest

2. Great barrier reef

Mixed dipterocarp forest

Dipterocarps are in the rainforest in South East Asia → provides an important habitat for native species, nutritional support via fruits, pollen + nectar → being lost in order to provide timber + clear the land for agriculture → excessive deforestation is endangering native species + threatening the water security + food of the indigenous populations

Great barrier reef

Coral species form connected reefs that are impacted by changes in oceanic temperature/pH → coral polyps receive nutrition from photosynthetic zooxanthellae (algae) that live within the polyp’s endodermis → changes in ocean temp/pH may cause zooxanthellae to leave the coral tissue, leading to coral bleaching → greenhouse gas emissions are increasing oceanic temp. + decreasing pH (ocean acidification) → mass bleaching of the Great Barrier Reef

Species richness

no. of different species present in an area (more species = greater richness)

Species evenness

relative abundance of the different species in an area (similar abundance = more evenness)

Ecosystem stability

requires a high level of both species richness + evenness in order to resist environmental change

Evidence for biodiversity crisis

assessments are based on repeated surveys + may rely on contributions from both expert scientists + members of the public (citizen scientists)

Causes of the biodiversity crisis

1. Overexploitation

2. Urbanisation

3. Deforestation

4. Pollution

5. Climate change

6. Global transport

Overexploitation

Overfishing + excessive or unnecessary hunting may reduce population numbers below sustainable levels

Urbanisation

Human construction can lead to a direct loss/fragmentation of habitats → increased competition between native species

Deforestation

The clearing of land for industry or agriculture → consequent loss of native habitat

Pollution

Microplastics, fertilisers + organic waste products → causes ongoing damage to natural environments

Climate change

Greenhouse gases released via industrial processes are changing climate conditions + increasing ocean acidification

Global transport

Globalisation is increasing the spread of pests, pathogens + invasive species

Conservation

protection + maintenance of natural resources → e.g trees, water + wildlife in order to preserve biodiversity

In-situ conservation

preservation of a species within their natural habitat (on-site)

In-situ conservation methods

• ecological monitoring

• legislation

• rewilding

• reclamation

Ecological monitoring

monitoring of species to ensure viable population levels are maintained

Legislation

ensures adequate funding for policing (no hunting) + education

Rewilding

active or passive restoration of damaged ecosystems to the point where they become sustainable

Reclamation

the repurposing of an area that has been utilised for human activity in order to restore previously existing ecosystems

Pros of in-situ conservation

• access to natural habitat → develop natural behaviour

• protects many species at once

• less expensive

Cons of in-situ conservation

• controlling exploitation is difficult

• needs extensive restoration

• population may drop during restoration

Ex-situ conservation

preservation of species outside their natural habitats (off-site)

Ex-situ conservation methods

• captive breeding

• botanical gardens

• seed/tissue bank

Captive breeding

animals being raised + bred in containment (e.g. zoos) to ensure survival prospects

Botanical gardens

areas devoted to the collection, cultivation + display of a wide variety of plant species

Seed/tissue bank

secure sites that store + catalogue seeds/tissue samples to preserve the genetic diversity of species

Pros of ex-situ conservation

• greater controlled environment

• improves chances of successful breeding with artificial methods

Cons of ex-situ conservation

• does not prevent damage of natural habitats

• species less likely to be reintroduced to the while

• increase in inbreeding

How to prioritise conservation

EDGE of existence selects highly endangers species (who satisfy both ED and GE)

Evolutionary distinct (ED)

species who have few close relatives and have unique phylogenic branches

Globally endangered (GE)

species at high risk of extinction according to the IUCN Red List

Ecosystem

a community of organisms interacting with each other and with their abiotic environment

Habitat

the place in which a community, species, population or organism lives

Geographical locations

where it is geographically → e.g. tropical environments exist at the equator

Types of habitats

the type of habitat → e.g. grassland environments are found at diverse locations

Challenges in a sand dune

• shifting sands

• lack of water

• exposure to wind + heat

• high levels of salt

How marram grass is adapted to sand dunes

Feature	Function
curled leaves	decreases stomata’s exposure to external air → reduces transpiration
deep tap roots	improves anchorage + access to deeper water reservoirs
stomata are sunk in pits	better traps water vapour → reduces transpiration
grass’s low growing	reduces exposure to wind + improves anchorage
horizontal underground stems (rhizomes)	maximises root penetration + stabilizes plant

Challenges in a mangrove

• high salt environment

• water logged soil

• low amount of oxygen available

How mangrove tress are adapted

Feature	Function
pneumatophores	roots 25-30cm above surface → obtains oxygen as they have spongy tissue within the many air spaces → oxygen enters through lenticles (pit) in the root
suberin coating on root cells	excludes majority of salt from the water taken up by roots
prop roots	provides stability
cable roots from the trunk	below surface → provides stability with fine-feeding tubes
propagule	developed for seedlings adapted in water dispersal

Limiting factor

component of an ecosystem which limits the distribution or numbers of a population

Abiotic factors that affect plants

• light intensity

• soil pH + mineral ions → affects plants ability to grow + reproduces

• wind speed + humidity → water loss + desiccation (complete removal of moisture)

• CO2 + O2 concentrations → rate of photosynthesis + aerobic cell respiration

• temp → influences rate of enzymes-catalyse reactions

Abiotic factors that affect animals

• wind speed + humidity → water loss + desiccation (complete removal of moisture)

• CO2 + O2 concentrations → rate of photosynthesis + aerobic cell respiration

• temp → influences rate of enzymes-catalyse reactions

Law of tolerance

populations have optimal survival conditions within critical minimal + maximal thresholds

Optimal zone

Central portion of curve which has conditions that favour maximal reproductive success + survivability

Zone of stress

Regions flanking the optimal zone, where organisms can survive but with reduced reproductive success

Zone of intolerance

Outermost regions in which organisms cannot survive (represents extremes of the limiting factor)

How to measure a specie’s abundance

• transect

• kite

Transect

straight line along an abiotic gradient from which population data can be recorded (using quadrats) to determine a pattern

How to analyse transect data

Measure an abiotic factor (e.g. temperature, light intensity or soil pH) at intervals along a transect + compare it with species abundance/distribution to identify correlations

When is transect used

assess species distribution in correlation with any abiotic factor that varies across a measurable distance

Kite graphs

relative width of each ‘kite’ represents the abundance of an organism at a particular point along a transect

When are kite graphs used

used to represent changes in species distribution in a clear + effective fashion

Conditions required for coral formation

• water depth

• pH

• salinity

• clarity

• temperature

water depth

shallow waters (60m) where they have light

pH

slightly alkaline (8pH)

salinity

salty water (23-42 ppt)

clarity

clear enough for light to penetrate

temperature

20-28C

What are the factors affecting the distribution of biomes

temperature + precipitation

Whittaker graph

Biomes

groups of ecosystems with similar communities due to similar abiotic conditions + convergent evolution

Characteristics of a tropical forest

• hot climate

• very high levels of precipitation

• very high levels of diversity in animal + plant species

Characteristics of a temperate forest

• moderate temperatures

• clear seasonal changes

• Deciduous trees are dominant → fertile soil

• high level of biodiversity

Characteristics of a taiga

• cold + icy

• small amount of precipitation (but high snow fall)

• dominated by coniferous trees

• little variation in species

Characteristics of a grassland

• moderate temperatures with wet + dry seasons

• consist of grazing animals + some predators

Characteristics of a tundra

• freezing temperatures

• very little precipitation

• Vegetation consists of low growing plants

• low levels of hibernating/migrating animal species

Characteristics of a hot desert

• experience extreme temperatures

• very low precipitation m

• minimal rainfall

Kapok tree adaptations

Feature	Function
buttress roots	spreads from the tree’s base → supports height as trees grow rapidly for sunlight
drip tip leaves	excess rainwater falls off quickly → prevents mold from growing in humid climate
waxy leaves	reduces transpiration loss → reflects sunlight

Spider monkey’s adaptations

Feature	Function
prehensile tail	acts a limb → allows it to grip branches whilst climbing and hanging
long strong limbs + flexible joints	swings easily between trees → moves quickly without touching forest floor

Saguaro’s adaptations

Feature	Function
widespread shallow roots	extend far near surface to absorb water quickly after rain
spines instead of leaves	reduce water loss through transpiration → protect against herbivores
succulent stem	stores large amounts of water during rare rainfalls → survival through dry periods

Fennec foc’s adaptations

Feature	Function
large ears	radiate heat to cool body → improve hearing to detect prey underground
light coloured fur	reflects sunlight and → provides camouflage against sand
burrow system	cools body → offers protection from predators + sun

Ecological niche

the role of a species or abiotic or biotic factors in an ecosystem

Abiotic factors

habitat in which an organism lives + the resources within the environment → e.g. light, temperature

Biotic factors

activity patterns of the organism + its interactions with other species → competition, predation

Examples of a bird’s niche componenets

Different forms of cells respiration that organisms may carry

• obligate anaerobes

• obligate aerobes

• facultative anaerobes

Obligate anaerobes

single celled organisms that only carry out anaerobic respiration → they cannot survive in the presence of oxygen

Obligate aerobes

organisms that cannot survive in the absence of oxygen → they rely on aerobic respiration to produce ATP → may be able to carry out anaerobic respiration in conjunction with aerobic respiration, but cannot survive on anaerobic respiration alone

Facultative anaerobes

normally respire aerobically, but can fully switch to anaerobic respiration in the absence of oxygen → can tolerate oxygen but also experience no long-term negative effects from its absence

Autotrophs

producers → make organic molecules from simple inorganic molecules

How do autotrophs get energy

Through photosynthesis → e.g. of organisms: plants, algae, several groups of photosynthetic prokaryotes

Heterotrophs

Consumers

How do heterotrophs get energy

they obtain their organic molecules from other organisms via:

• holozoic

• saprotrophic

Holozoic nutrition

organic matter is ingested and then digested internally, before being absorbed and assimilated

Ingestion

The taking of food into the digestive system through the mouth