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Download Lecture 5: Animal adaptations to the environment
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Animal adaptations Outline: • Acquisition of energy and nutrients • Respiration • Homeostasis • Water balance • Biological rhythms • Readings: Chapter 7 Energy and nutrient acquisition Detritivores Herbivores Types of herbivores • • • • • • Grazers - leaf tissue Browsers - woody tissue Granivores - seeds Frugivores - fruit Nectivores - nectar Phloem feeders - sap • High cellulose (fiber), low protein • Animals can’t digest cellulose (no cellulase enzymes) • Need symbiotic bacteria, protozoa Ruminants (e.g. cows, sheep, deer) Non-ruminants (e.g. rabbits, horses) Coprophagy = ingestion of feces • E.g. Lagomorphs (rabbits, hares & pikas) • E.g. Detritivores N and food quality • For herbivores, food quality increases with increasing N content • In animals, C:N ~ 10:1 • In plants, C:N ~ 40:1 herbivores limited by N availability – Highest in growing stems, leaves, buds – Decreases as plant ages Herbivores usually born in spring Carnivores • Composition of food similar to own tissues --> simple stomach --> small caecum • Need to get enough food Omnivores • Feed on > 1 trophic level, e.g. plants and herbivores • Diet varies with season, life cycle Diet breadth 1. Generalists: “polyphagous” – eat >1 prey species 2. Specialists: “monophagous” – eat one prey species – or eat specific part of prey • • E.g. seed-eating birds Specialists are usually • • Short-lived (active only when food is available) Highly adapted to a specific food type (can’t use any other) RESPIRATION C6H12O6 + 6O2 6CO2 + 6H2O + ATP HOMEOSTASIS THERMOREGULATION TEMPERATURE REGULATION TYPE OF HEAT PRODUCTION: Endothermy: - heat from within Ectothermy: - heat from without Heterothermy - employ endo and ectothermy in different situations TEMPERATURE VARIATION: Homeothermy - constant temperature Poikilothermy - variable temperature TEMPERATURE REGULATION poikilotherms TEMPERATURE REGULATION poikilotherms Operative temperature range TEMPERATURE REGULATION poikilotherms Acclimatization TEMPERATURE REGULATION poikilotherms Lizards and snakes: body temperature varies only 4-5oC/day TEMPERATURE REGULATION homeotherms Endothermy – ectothermy tradeoffs Endothermy tradeoff Conserving energy – ectothermy for juveniles Because of their small size (high surface: volume ratio) and their need to invest energy in growth, juvenile birds and mammals are often ectothermic, obtaining heat from their parents. Conserving energy – hibernation Bears are not true hibernators; their body temperature drops only a few degrees, and they are relatively easily awakened Conserving energy – countercurrent heat exchange without with Releasing energy – countercurrent heat exchange RETE Adaptations to aridity and heat Water balance in aquatic environments • Freshwater organisms: hyperosmotic (water wants to move inside of organism • Marine organisms: hypoosmotic (water wants to move outside of organism Controls on activity Human diurnal cycle Life history strategies Outline: • Types of reproduction • Mating systems • Sexual selection • Energy and timing of reproduction • Offspring • Habitat selection • Environmental influences • Readings: Ch. 8 A simple life history Life history = schedule of birth, growth, reproduction & death Types of reproduction • Asexual or sexual • Different forms of sexual reproduction Simultaneous hermaphrodites Sex change Mating system • Strength of bond: – Monogamy (strong) - Promiscuity (no bond) • Types of bonds: – Monogamy (one-to-one) – Polygamy (one-to-many) • Polygyny (one male, many females) • Polyandry (one female, many males) POLYANDRY: African Jacana Sexual selection • Intrasexual selection – male-to-male or female-to-female competition for the opportunity to mate Sexual selection • Intersexual selection – differential attractiveness of individuals Reproduction is costly Timing of reproduction • Semelparity - reproduce once and die • Iteroparous - reproduce throughout lifetime European grasshopper, Chorthippus brunneus An iteroparous summer annual Pigweed, Chenopodium album A semelparous summer annual Semelparous perennials Coho salmon: a long-lived semelparous animal • Dies after spawning (2-5 yrs) • Overlapping generations Semelparous perennials Bamboo • Both genets and ramets are semelparous. • Genets can live for 200 years before the simultaneous flowering of all ramets. Parental investment Fecundity Fecundity Reproductive tradeoffs Reproductive tradeoffs Reproductive tradeoffs Reproductive tradeoffs r and K strategists For next lecture: • Please read Chapter 9, 10, 11, 12 65
