Year 9 Biology: Organisms respond to their environment

1. Temperature control

1.1. Ectotherms

1.1.1. Defintion: An animal that relies on an external source of heat

1.1.2. Warm up by basking in sun

1.1.3. Cool down by seeking shade

1.1.4. Examples

1.1.4.1. Crocodile

1.1.4.2. Snake

1.1.4.3. Lizard

1.2. Endotherms

1.2.1. Defintion: An animal that generates its own body heat metabolically

1.2.2. Examples

1.2.2.1. Mammals

1.2.2.2. Most birds

1.2.3. Mechanisms

1.2.3.1. Vasoconstriction

1.2.3.1.1. Defintion: Narrowing of blood vessels

1.2.3.1.2. Increases blood flow to surface for heat loss

1.2.3.1.3. Helps cool body down

1.2.3.2. Vasodilation

1.2.3.2.1. Defintion: Widening of blood vessels

1.2.3.2.2. Decreases blood flow to surface

1.2.3.2.3. Helps conserve body heat

1.2.3.3. Sweating

1.2.3.4. Panting

1.2.3.5. Shivering

2. Plant tropisms

2.1. Phototropism

2.1.1. Response to light

2.1.2. Stems grow towards the light source

2.2. Geotropism

2.2.1. Response to gravity

2.2.2. Positive geotropism

2.2.2.1. Root tips grow towards pull of gravity

2.2.3. Negative geotropism

2.2.3.1. Stems grow away from pull of gravity

2.3. Hydrotropism

2.3.1. Response to water availability

2.3.2. Plant roots grow towards soil with higher moisture content