subject guide notes

B4.1.1—Habitat as the place in which a community, species, population or organism lives

habitat can be defined as a geographical or physical location that provides organism with the resources it needs to survive

B4.1.2—Adaptations of organisms to the abiotic environment of their habitat

adaptations can occur randomly through mutation, or can be due to selective pressures in environment

adaptation plays a role in evolution

Marram grass is a type of grass that has adaptations, which allow it to survive on sand dunes

  • has deep root system that enables it to access water & nutrients - resists drought

  • can tolerate high levels of salt in sand

  • has strong roots, which anchor it in the sand

    • the roots also prevent erosion of the sand

  • leaves are rolled, so stomata are tucked away

Rhizophora apiculata has adaptations that allow it to survive in mangrove forests

  • is a halophyte, so it can tolerate high levels of salt in water

  • roots hv structures called pneumatophores, which provide the roots with oxygen when the soil is waterlogged

  • hv stilt roots that keep tree above water, meaning it can survive floods

  • propagates by the seeds germinating & begin to grow while still attached to the parent tree. this means that the seeds are not dispersed by water

B4.1.3—Abiotic variables affecting species distribution

adaptions of a species gives it a range of tolerance

abiotic variables for plants can be temperature, light intensity, pH of soil, availability and location of water

abiotic variables for animals can be breeding sites, geographical factors, light intensity, food, water, etc

B4.1.4—Range of tolerance of a limiting factor

range of tolerance is often determined by limiting factors

if organisms exceed their range of tolerance, they may experience stress of death

if environmental conditions exceed an organism’s range of tolerance, they may not be able to reproduce successfully or survive

range of tolerance be affected by environmental changes, such as pollution & climate change

transect lines is a technique used for sampling

B4.1.5—Conditions required for coral reef formation

are an example of a marine ecosystem

water depth - can grow in shallow waters, where sunlight can reach them & support growth of algae

pH - between 8.0 - 8.4 (slightly alkaline)

salinity - stable salt concentration

water clarity - clear water so that maximum sunlight can penetrate

  • this is cuz algae (zooxanthellae) reside in coral, and help coral remove waste & produce oxygen and food. the coral shelters the algae & provides it with the compounds it needs for photosynthesis

temperature - cant withstand water temps higher than 18degrees

B4.1.6—Abiotic factors as the determinants of terrestrial biome distribution

for any given temp & rainfall pattern, one type of ecosystem will likely develop

2 main abiotic factors that determine the type of biome that exists in a specific region:

  1. temperature - affects rate of biological processes (such as photosynthesis, metabolism, and growth)

  2. rainfall - determines availability of water, which is instrumental for survival

same biome can occur in geographically different locations with similar climates

temperature vs. rainfall graph can illustrate relationship between temp & precipitation

B4.1.7—Biomes as groups of ecosystems with similar communities due to similar abiotic conditions and convergent evolution

tropical forest

  • characterized by high temp

  • high precipitation & light intensity

  • low seasonal variation (relatively constant climate throughout year)

grassland biome

  • temp - moderate to high

  • low to moderate precipitation

  • high light intensity

  • high seasonal variation (hot summers & cold winters)

taiga biome

  • low to moderate temp

  • moderate precipitation

  • low to moderate light intensity

  • high seasonal variation (long, cold winters and short, cool summers)

temperate biome

  • moderate temp

  • moderate to high precipitation

  • moderate light intensity

  • moderate seasonal variation(less pronounced seasons)

tundra biome

  • low temp

  • low precipitation

  • moderate to high light intensity

  • high seasonal variation (long, cold winters and short, cool summers)

desert biome

  • high temp

  • low precipitation

  • high light intensity

  • low (slight variations in temp & rainfall throughout year)

B4.1.8—Adaptations to life in hot deserts and tropical rainforest

Xerophytes have adaptations that allow them to live in deserts

animal - Gila monster

  • bumpy skin to retain moisture

  • can store fat in tail, allowing it to survive long periods of time without food

  • slow metabolic rate - can survive long periods of time without food or water

  • powerful jaws & poisonous saliva, meaning it can overtake prey and survive

  • venom causes pain in prey

plant - Ocotillo

  • deep root system - access water deep within soil

  • horizontal root system - can absorb small amounts of precipitation

  • greenish chlorophyll-containing bark allows it to carry out photosynthesis without presence of leaves

  • vibrant red flowers to attract pollinators for reproduction

rainforests hv high amounts of rainfall & warm temps, which creates a humid atmosphere

animal - Harpy eagle

  • strong talons to crush skulls of prey

  • broad & strong wings to easily fly through forest, and to silently glide

  • sharp beak to capture & feed on prey

  • strong & sensitive hearing to hear prey moving through forest

  • binocular visions to estimate distance & track fast-moving prey

plant - Giant Amazon Water Lily

  • large circular leaves that hv a waxy coating which helps repel water, allowing the Lily to float on water surface

  • root system that anchors Lily to bottom of river & extract nutrients from its soil

  • large flowers open at night & emit strong fragrance to attract pollinators