Physiological (function) adaptations for survival

Physiological adaptations An animal’s physical ability to deal with its environment determines whether it is able to survive there Nervous system and reflexes Hormonal Regulation of water balance and temperature

Water balance in small desert animals Tarrkawarra (Spinifex mouse) Metabolic water available for use in mouse Water in food – depends on food source Free water (dew/rain) may be very little or none Very little water in faeces Very little water content in urine Some evaporation from skin – minimised by huddling in burrows Loss in exhaled air WATER IN WATER OUT

Homeostasis Homeostasis is a body keeping the INTERNAL environment constantly within a tolerable range, despite EXTERNAL environmental changes.

Tolerance levels in humans Temperature: 36.1 – 37.8 degrees Celsius Blood glucose – 3.6 – 6.8 mmol per L Water – intake must balance loss Ions (e.g Ca2+ in plasma) – 2.3 – 2.4 mmol per L pH of arterial blood – 7.4 (for enzyme action) Blood pressure – relaxed: 13.3 kPa. Contracted: 5.33 kPa. Urea in plasma - <7mmol per L

Other organisms have tolerance levels too! Plants must regulate water balance and concentration of gases such as carbon dioxide and oxygen

Systems contribute to homeostasis Body systems help to regulate critical tolerance levels Endocrine system – hormones Nervous system Behaviours can assist in homeostasis too (eg. Getting a thicker blanket on a cold night, drinking water habitually with meals)

Questions etc pg 301 Quick Questions Glossary words: homeostasis, tolerance range, limiting factor

Keeping it all the same The nervous system and the endocrine system work together to perform homeostasis Nervous system detects change Endocrine system responds to change

The Nervous System

The response system Detection of change by affector neurons Change message decoded in CNS Effector neurons send response message back to area of change