Lecture 22 - Terrestrial Adaptations
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elizabethmg on June 20, 2012
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18 terms
Terms | Definitions |
|---|---|
 Silurian (+/- 420 mya) | First arthropods colonized land habitats, mainly through intertidal habitats. -Spiders, centipedes and mites: first land arthropods. |
| Carboniferou. (+/- 300 mya) | Amniotic egg evolved. -Independent of water to complete their life cycles. -Allowed them to colonize land habitats. -"true terrestrial" animals. |
| Four main categories of terrestrial animals (based on their dependence to water): 1). Interstitial Fauna | -Live on or in the soil. -Small animals, permanently surrounded by a film of freshwater - not much different from freshwater animals. (e.g. nematode worms, rotifers mites). |
| Four main categories of terrestrial animals (based on their dependence to water): 2). Cryptozoic Fauna | -Live on or in the soil. -Larger in size, not continuously covered with moisture but live in zones of continuously high humidity. (e.g. earth worm, centipedes, many larval insects). |
| Four main categories of terrestrial animals (based on their dependence to water): 3). Hygrophilic Fauna | -Wet Loving. -Need water supply of high humidity for activity - depend on water in their environment and have strategies for survival in conditions of water shortages (e.g. snails, slugs and amphibians). |
| Four main categories of terrestrial animals (based on their dependence to water): 4). Xerophilic Fauna | -Dry loving. -All animals that can be active in dry conditions - independent from water for their entire life cycle (e.g. insects, arachnids, reptiles, birds, mammals). |
| What challenges do animals face on land? | 1. In air, animals will always tend to loose water and salts. 2. Water is 1000 times more dense than air. 3. Reduced viscosity in the air = movement of land meets with less resistance from the medium = 'easier' to move on land, and can achieve greater speeds. 4. Temp. much more variable on land = greater instability and unpredictability in air. 5. O2 levels are much higher and more readily available in the air. |
| 1). Behavioural Regulation of Water Balance | -Mainly found interstitial, cryptozoic and hygrophilic (moist-skin) animals: survive on land because of their ability to find and remain in habitats of high humidity. |
| 2). Reduce Permeability of Skin and Respiratory Surfaces | -In some of the moist skin animals: -Land snails = retreat fully into their shells and seal off opening. -Waxy tree frog in Central and South America = specialized gland that secretes wax over the skin. |
| 2). Reduce Permeability of Skin and Respiratory Surfaces: Insects and Arachnids (xerophylic) | -Acquisition of a lipid barrier in the epidermis to form a cuticle and wax. -Carapace and respiratory organs lined with chitin. |
| 2). Reduce Permeability of Skin and Respiratory Surfaces: Lizards and Snakes (Xerophylic) | -Lipid barrier + high [conc] of Keratin (protein) in epidermis. -Together w/ insects and spiders = champions of impermeability amongst animals. |
| 2). Reduce Permeability of Skin and Respiratory Surfaces: Endothermic mammals (xerophylic) | -Lipid barrier + high [conc] of protein Keratin in epidermis but interrupted by glandular pores (sweat glands) as cooling mechanism. -Epidermis not as impermeable as lizards, snakes, insects and spiders = use regulatory organs. |
| 3). Regulatory Organs | -Some birds and all mammals: Loop of Henle (kidney) to help regulate water/salts. =1 descending and 1 ascending portion. =counter-current: water and/or ions can be re-absorbed before leaving body as urine (e.g. when animal is water stressed). |
| Adaptations to heat gain/loss: | 1). Basking or burrowing. 2). Shivering: to produce heat from muscle contractions. 3). Non-shivering thermogenesis: release of heat from "futile cycling" of metabolic substrates. 4). Evaporative cooling (when concurrent water loss can be tolerated). 5). Heat conservation by vascular control: reduces blood flow to specific regions to maintain activity at cold temps, or increase blood flow to peripheries of the body to dissipate heat. |
| To protect the gametes, eggs and embryos from desiccation: 1). Species that have a marine or interstitial ancestry: To protect the Gametes - | -Use sperm droplets and protective spermatophores (many spiders & insects). -Return to the water and mate/spawn (most crabs & amphibians). |
| To protect the gametes, eggs and embryos from desiccation: 1). Species that have a marine or interstitial ancestry: To protect the eggs/embryos - | -Insects and most other arthropods: eggs with stiff chitinous cuticle (often with a waxy layer). -Most insects also lay their eggs in a specific protected spot (w/c will also provide food source for larvae): *on leaf, flower or tree bark *in the flesh of another animal *underwater -Spiders and other arachnids: *lay their eggs in nests *carry eggs with them: "egg sac" *Some ground or brood their eggs |
| To protect the gametes, eggs and embryos from desiccation: 2). Species that have a freshwater ancestry: Amniotes-Cleidoic Egg: | -Shell: hard or leathery, and porous -Yolk (to feed developing larva) -Internal membranes that allow the mebryo to breathe but keep the water in. -Frees parents from any dependence on water at the site of mating or where the eggs are laid. |
| To protect the gametes, eggs and embryos from desiccation: 2). Species that have a freshwater ancestry: Marsupial & Placental mammals - | 1) Embryo development is internal. 2) Females feed young with breast milk. |
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