WJEC A Level Biology: Adaptations to Nutrition and Digestive Systems

Autotrophic

Organisms which use carbon dioxide and water (inorganic molecules) to synthesise organic compounds.

Photoautotrophic

Organisms which obtain their nutrition through photosynthesis.

Chemoautotrophic

Organisms which obtain their nutrition through inorganic molecules, such as sulphur.

Heterotrophic

Organisms which feed on organic compounds produced by other organisms.

Saprotrophic/saprobiotic

Organisms which secrete enzymes, externally digest food substances and then absorb the products of digestion into the organism, e.g. fungi.

Holozoic

Organisms which internally digest food substances, e.g. animals.

Parasitic

Organisms that live on or in a host.

Simple, undifferentiated sac-like gut

A type of digestive system, e.g. found in Hydra.

Tube guts

Digestive systems with different openings for ingestion and egestion and specialised regions for the digestion of different food substances.

Unicellular organisms

Organisms like Amoeba that absorb food particles and carry out digestion intracellularly.

Different enzymes

Required for the digestion of different foods, e.g. protease, lipase.

Different conditions

Different pH levels are necessary as different enzymes have different optimum pHs.

Human gut

Adapted to an omnivorous diet, which includes both plant and animal materials.

Amylase

An enzyme present in the saliva of most humans to digest carbohydrates, characteristic usually found in herbivores.

Duodenum

The first section of the small intestine where proteins and lipids are broken down and contains Brunner's glands.

Brunner's glands

Glands that produce mucus which protects the duodenum and maintains an alkaline pH.

Ileum

The last section of the small intestine, which lacks Brunner's glands.

Folded walls and villi

Features of all sections of the small intestine that increase surface area.

Herbivore guts

Adapted to a plant-based diet with strong, flat molars for grinding leaves.

Ruminants

Mammals that digest food by fermentation in their stomachs prior to digestion via microbe action.

Four areas of ruminant stomach

Rumen, reticulum, omasum, and abomasum.

Carnivore guts

Adapted to a meat diet with large canines and a much shorter gut.

Parasites

Highly specialised organisms that obtain their nutrition at the expense of the host species.

Tapeworms (Taenia spp.)

Parasites that live in small intestines and feed off the food the host eats.

Sucking lice (Pediculus spp.)

Parasites that live on fibres and feed off their host's blood.