Animal digestion and feeding strategies Flashcards
(16 cards)
Digestive systems in invertebrates
Blind guts are incomplete digestive systems
Bivalve digestive systems
Eg insects or starfish
What is suspension feeding?
Common in aquatic organisms
Feeding on organisms that are very small in comparison to the size of the feeding animal
Includes feeding on organisms lower on the food chain resulting in a higher amount of energy available
Includes bivalves like mussels
Also whale sharks, basking sharks and baleen whales
Feeding on organisms that are individually targeted
Requires that prey is located identified, subdued and ingested
These mechanisms include herbivores (grazing mammals, nectar feeding insects, gastropods) and carnivores (carnivorous fish, birds of prey)
Some of these organisms use toxic compounds to subdue or kill their prey (scorpions, spiders, jellyfish and snakes)
Symbiosis feeding mechanisms
Autotrophic microbes
Heterotrophic microbes (gut microbiome)
Photoautotrophic microbes (reef corals)
Chemoautotrophic microbes (hydrothermal vent species)
Diversity in digestive systems in vertebrates
Tounge, teeth and salivary glands
Ceca (blind pouches) and intestines are important in non-ruminant herbivores, used for cellulose digestion and houses microorganisms
Some animals have a crop which for example is used as food storage in birds
Stomach, gizzards and rumen
Herbivore adaptations
Animals don’t produce cellulase so herbivores rely on symbiotic microorganisms in the gut
Foregut fermenters
4-chambered stomach
In ruminants the stomach is enlarged and divided into 3 non-absorptive chambers and the true stomach
In non-ruminants there’s a singular enlarged stomach
No need to chew thoroughly
Slow passage of food
Cellulose is broken down before the small intestine
Lophed teeth and dental durability
Enamel wears off the top of the ridges which exposes dentin resulting in sharp enamel blades
Only one set of replacement teeth, often highly abrasive food
Adaptations of this include the crown extending deep into the jaw bone, sometimes cementum covers the whole tooth, often very deep lower jars
When teeth wear out an animal can no longer feed
The exception is in elephants, there are 6 sets of molars to replace lost ones
Hindgut fermenters
Smaller stomach in comparison to other mammals, enlarged cecum and intestine (koala, rabbits, horses)
They rely on thorough chewing
Nutrients are absorbed in the stomach and small intestine
Some loss of energy in faeces
Cellulose is attacked in the cecum and large intestine
Coprophagy in small herbivores
Types of carnivorous predators
Predators need intelligence, good sense, stamina, physical strength
Sit and wait predator is typically solitary and territorial, profitable when prey is common and mobile
Search and chase predator often hunts in packs, or sometimes solitary, pursuit is long and lengthy
Scavenger predators feed on dead animal or plant material, opportunistic, hunt in packs, scavenge solitary
Advantages of lactation
Minimising energy costs to the mother while maximising the newborn’s survival
Rapid growth
Sustains a high metabolic rate
Taste preferences (learning which food is safe)
Social bonds and learning
Composition of milk
Varies, even within an individual due to circadian rhythm and depending on the lactation stage
Foremilk (high water content) versus hindmilk
Between species, growth rates and environmental conditions
Water, fat, carbohydrates, lactose, proteins and minerals
The milk of mammals with rapidly growing young contain much more protein and fats
The mammary gland
Preparation for lactation happens during gestation
Hormones stimulate gland development (oestrogen, progesterone, prolactin)
Lactation is prevented during pregnancy through high levels of oestrogen and progesterone
Birth leads to an abrupt decline in these hormones (loss of placenta)
Characteristics related to lactation and suckling
Secondary (hard) palate
Soft tissue/cheeks
Two generations of teeth/delay or permanent tooth eruption
Quick and steady growth of endothermic babies (high energy demand/metabolic right)
Increased flexibility from a reduction in cervical ribs
Parental care - learning of essential and complex adult skills
Postnatal growth rates
Body size - small mammals generally grow faster due to a faster metabolic rate, exceptions are small mammals with a low metabolic rate
Related to life history, for example preparing for hibernation
Lactation and water balance
Substantial water loss
Highly concentrated milk
Water recycling by ingesting the young’s urine and faeces
Marsupials - long lactation period, milk is supplied only to teats with attached young, double suckling may occur
Placental mammals - short lactation period, milk production maintained in multiple teats
