VCE Biology Unit 2 Area of Study 01 Adaptations of Organisms

1. VCE Biology Unit 2Area of Study 01Adaptations of Organisms Living in extreme terrestrial environments

2. Living in extreme terrestrial environments Desert • Low rainfall • High level of evaporation • Hot (Australia, Sahara) or cold (Central Asia, South America, Antarctica) Antarctica largest desert – 50 mm rain per year, 14,245,000 km2 Sahara largest ‘hot’ desert 9,000,000 km2

3. Living in extreme terrestrial environments Australia has greatest percentage of continent as desert/semi-arid (44% and 37% respectively) • High temperature • High solar radiation • Low rainfall

4. Living in extreme terrestrial environments Animals Stress • Body temperature • H2O • Salt balance

5. Living in extreme terrestrial environments Survival • Regulate these factors or tolerate extreme fluctuations

6. Living in extreme terrestrial environments Temperature regulation assisted by • Behaviour that increases or decreases heat exchange with external environment. • Circulatory adjustments alter blood flow through skin – alters heat exchange • Increase or decrease production of metabolic heat. • Evaporative cooling through sweating or panting (trade off with water loss)

7. Living in extreme terrestrial environments Reptiles • Behaviour changes most important to regulate rate of heat exchange Behavioural Thermoregulation • e.g. Australian agamid lizard, Shark Bay, WA

8. Living in extreme terrestrial environments • Some iguanid lizards maintain body temperature at ~38°C for extended periods. • Desert snakes and tortoises maintain body temperature at ~30°C adopt nocturnal behaviour during summer

9. Living in extreme terrestrial environments Sleep through bad times Some animals survive harsh conditions by going into torpor or hibernation. Torpor (fish, frogs, lizards, birds, bats and mice) allow body temperature to decrease and become inactive or dormant.

10. Living in extreme terrestrial environments Frogs burrow into sand during dry season and become dormant Water holding frog burrows deep into sand and makes a cocoon from its cast off skin and can survive for months.

11. Living in extreme terrestrial environments Escaping the cold – hibernation Do any Australian animals hibernate? Short beaked echidna goes into torpor underground to escape winter/snow in southern mountains.

12. Living in extreme terrestrial environments Hibernation • Long term torpor • Happens at onset of winter • In den/burrow • Decrease energy requirements (do not eat) • Hibernation saves 60% of an animal’s annual energy requirement • Some evidence suggest animals may live longer.

13. Living in extreme terrestrial environments Triggers for Hibernation. One of more factors • Scarcity of food • Decrease in temperature • Endocrine response to change in daily light cycle. • Mammals and birds enter hibernation from sleep and involve decrease of body temperature close to ambient, but never below zero

14. Living in extreme terrestrial environments Triggers for Hibernation. One of more factors • Burrows/dens temperature constant • Metabolism decreased (indicated by decrease in O2 consumption – leads to fall in body temperature • Heart rate decreases to around 3 to 10 beats per minute • Respiration decrease • Slow breathing with long periods of no breathing

15. Living in extreme terrestrial environments Plants in arid environments Adaptations for reducing water loss • Xenophytes (‘lovers of dryness’) • Two types • Flesh succulent plants (e.g. cacti) • Hard-leaved plants called sclerophylls

16. Living in extreme terrestrial environments Adaptations for reducing water loss • Thick waxy cuticle • Hairs covering leaves • Few stomata • Sunken or protected stomata • Reduced leaf surface area to volume • Orientation of leaves away from direct rays of sun

17. Living in extreme terrestrial environments Leaf cuticle and hairs • Xerophytes have thick waxy cuticle impermeable to water • Hairs reduce leaf temperature and water loss

18. Living in extreme terrestrial environments Distribution of Stomata • Fewer stomata. Number and size varies between species. • Pits surrounded by hairs • Maybe closed at hottest time of day • Succulents close stomata at day and open at night for uptake of CO2

19. Living in extreme terrestrial environments Reduced surface area and leaf orientation • Surface area low to reduce water loss by transpiration • Some species have needle like leaves (e.g. Hakea and cacti) • Eucalypts’ leaves hang vertically. Stomata and photosynthetic cells on both sides of leaves (i.e. isobilateral).

20. Living in extreme terrestrial environments Coping with salinity on land • [Salt] can be 1/10 of sea water. Combined with high temperatures and low rain fall. • Creates osmotic stress due to lack of water

21. Living in extreme terrestrial environments Halophyte adaptations • Halophytes (‘lovers of salt’) tolerant to high levels of salt and many are succulents • Regulate water loss and salt accumulation in leaves from transpiration of water from roots.