Unit 1 – Unity and diversity AOS 2 – Functioning organisms

1. Unit 1 – Unity and diversityAOS 2 – Functioning organisms Chapter 5 Obtaining energy and nutrients for life

2. Heterotrophs and autotrophs All living organisms require nutrients in order to maintain normal bodily functions. Organisms can be classified based on the main way they obtain the nutrients they require for living. They can be classified into one of two groups: • Autotroph: an organism that is able to synthesise (make) their own organic compounds from simpler organic compounds. • Heterotroph: an organism that cannot synthesise organic compounds, but rather has to obtain them by eating other organisms.

3. Autotrophs • Autotrophs are organisms that synthesise the nutrients they require for energy. The process by which autotrophs obtain this energy is called photosynthesis. • As discussed in chapter 3, photosynthesis refers to a chemical reaction that converts the simple organic molecules water and carbon dioxide to energy rich organic compound glucose. • This glucose is then converted to a form of energy that cells are able to use, called adenosine triphosphate (ATP).

4. Photosynthesis in detail • Photosynthesis involves a series of complex biochemical reactions in which sunlight energy is converted to chemical energy in sugars. It occurs in the chloroplasts of plant and algae. • Photosynthesis involves two sets (phases) of reactions: • Light dependant phase – as the name suggests requires sunlight. • Light independent phase – occurs independent of light but depends on the products of the first light dependent phase.

5. Phases of photosynthesis • Phase (shift) 1 Inputs (reactants) – Sunlight, water (H20) and adenosine diphosphate (ADP) Outputs (products) – Oxygen, hydrogen ions (H+) and adenosine triphosphate (ATP) • Phase (shift) 2 Inputs (reactants) – Carbon dioxide (CO2), hydrogen ions (H+) and adenosine triphosphate (ATP) Outputs (products) – Glucose (C6H12O6) and adenosine diphosphate (ADP) • The hydrogen ions (H+) and ATP from shift 1 are used as the reactants for shift 2. Conversely, the ADP produced by shift 2 is used as a reactant in shift 1.

6. Worded reactions • Write a worded reaction for the: • Light dependent phase, and • Light independent phase. Answers: a) sunlight water + ADP oxygen + hydrogen ions + ATP chlorophyll b) carbon dioxide + hydrogen ions + ATP glucose + ADP • Write the summarised worded and chemical reaction for photosynthesis.

7. Plant structures and photosynthesis • Leaves: main structure for intake of CO2 through stomatal pores, contain many chloroplasts fro photosynthesis, flat shape increases SA:V to allow greater sunlight exposure, thinness of the leaf increases ability of gases to diffuse. • Stems: have two different types of vessels to transport different substances throughout the plant; • xylem transports water and minerals from roots to all parts of the plant above ground that need them, and • phloem transports glucose from photosynthetic tissues to non photosynthetic tissues. • Roots: covered in root hairs to increase the SA:V which water and dissolved minerals can be uptaken into the plant.

9. Revision tasks • Copy key ideas from page 100 into your exercise book. • Complete quick-check questions 1-7 from page 100.

10. Heterotrophs • Any organism that is unable to make their own organic material must obtain it from eating another organism. • Organisms that eat or consume other organisms in order to obtain nutrients required for living are called heterotrophs. • As a group, heterotrophs exploit a wide range of foods – plant matter, flesh of other animals living or dead, even faecal matter. • Read through ‘Changes through time’ and ‘Food from the bush’ pages 101-102.

11. Requirements for digestion • Some simple nutrients can be absorbed by the body, while other more complex compounds need to be broken down. • Digestion is the process by which food is broken down into simple compounds that can be utilised by the body. • Generally, four steps of digestion occur before a substance can become available for use by the cells of an animal: • Ingestion – intake of food into the mouth • Mechanical breakdown – break down of food involving moving parts of the body. Occurs in two parts, firstly by chewing in the mouth and secondly by the churning of the stomach, mixing the food around. • Chemical breakdown – secretion or various digestive enzymes onto the food particles to further break down food particles into smaller and smaller particles. • Absorption – organic molecules pass through the lining of the intestinal walls into the blood stream to be distributed to cells.

12. Mechanical breakdown of food • Jaws and teeth The jaws surround the mouth and are opened and closed by muscles. Teeth are the hard bony appendages found in the jaws of many animals. Movement of toothed jaws breaks food down into smaller pieces. The structure of the teeth and jaws relates to the diet of the animal. Example 1 – Tasmanian devils These animals are carnivorous, meaning they eat the flesh of other animals. This requires sharp teeth and strong jaws. Example 2 – Horses Horses are herbivorous, and have large flat teeth to grind the grass matter that they eat.

13. Kinds of teeth There are four different kinds of teeth found in most mammals: • Incisors: cutting/clipping teeth found at the front of the mouth, used predominantly by herbivores and omnivores. • Canines: well developed in carnivores, specialised for tearing flesh from bones. • Premolars: smaller than molars, flattened • teeth used for grinding food. • Molars: large flattened teeth used for grinding food. Figure 5.12 page 105 – Longitudinal section through a generalised tooth.

14. Differences in teeth arrangements Fig 5.14 on page 106 – Different teeth arrangements in some animals • Copy key ideas and answer quick check questions on p 106

15. The digestive system • Class task – group work presenting the different parts of a typical vertebrate digestive system • The mouth and oesophagus – 2 people • The stomach – 3 people • The liver and gall bladder – 3 people • The pancreas – 3 people • The small intestine (duodenum) – 3 people • The small intestine (jujenum and ileum) – 3 people • Absorption in the small intestine – 2 people • The large intestine, rectum and anus – 4 people

16. Digestion in herbivores • Herbivores are animals that only eat plant matter. Cellulose is the major carbohydrate found in plants, but it indigestible by animals. Cellulose can only be broken down (fermented) by bacteria, and so all animals that eat plant matter have bacteria living somewhere in their gut. • Depending on where the bacteria live in the gut, herbivores are classified into two groups: • Foregut fermenters or • Hindgut fermenters

17. Fermentation • Fermentation is the breakdown of cellulose cell wall of plant cells by bacteria to access the energy found within plant cell. • Foregut fermenters – the foregut is comprised of the oesophagus and the stomach. As bacteria need to live somewhere, foregut fermenters either have a modified stomach (known as ruminants) or a modified oesophagus ( non-ruminants). • Hindgut fermenters – the hindgut is comprised of the small intestine and large intestine. Hindgut fermenters either have a modified small intestine (caecum fermenters) or a modified large intestine (colon fermenters).

18. Figure 5.30 page 121 – Cow and koala; two different types of herbivores.

19. Digestion in nectar and pollen feeders • Some heterotrophs have highly specialised diets, eating the pollen or nectar from only one or two different species of plant. • Nectar is a sugary substance secreted by flowers to attract animals to feed and help disperse pollen to other plants when the animals move on. • As nectar is made of sugar, very little digestion needs to occur before the glucose can be absorbed into the blood stream. As such, the digestive tracts of nectar and pollen eaters are simple and short. This is also necessary as these animals are normally tiny in size.

20. Digestion in carnivores • Carnivorous animals are those that eat the flesh of other animals to obtain their energy and nutrients for living. • Carnivorous mammals do not generally eat any plant matter, and therefore, do not require complicated, modified digestive systems that are found in herbivores. • Similarly, the protein found in animal flesh is much easier to digest than cellulose, resulting in a fairly short and simple digestive system, often also characterised by a muscular stomach.

21. Figure 5.30 page 121 – Tasmanian devil (carnivore) and honey possum (nectar feeder)

22. Accessing the energy • Digestion of plant and animal materials results in simpler molecules, including glucose, being absorbed into the bloodstream and transported to all cells. • But organelles cannot utilise glucose as it is…what do they do? • The convert the glucose to ATP through a series of chemical reactions that occurs in the mitochondria. These reactions are referred to as cellular respiration, and the chemical equation can be summarised as below:

23. Questions and revision • Answer quick check questions 13-16 from page 123. • Answer Biochallenge questions 1-4 on page 125. • Answer the following chapter review questions from pages 125-127 2, 3, 4, 5, 6, 11, 12a, 13 and 14