Unit 1; Area of Study 2

Functioning Organisms

Chapter 5

Obtaining Energy and Nutrients for Life

WEEK 6: Obtaining NutrientsLEARNING OUTCOMESBy the end of this week, you should be able to

explain:Biochemical processes including photosynthesis and

cellular respiration in terms of inputs and outputs.Obtaining nutrients: organic and inorganic

requirements; autotrophs; heterotrophs.Obtaining energy: inputs and outputs of

photosynthesis; structural features of photosynthetic organisms.

Processing nutrients: features of effective systems in heterotrophs; examples of systems in different animals.

LESSONS 1-2: Heterotrophs, autotrophs and photosynthesisLEARNING OUTCOMESBy the end of these lessons, you should be able

to:Define ‘autotroph’ and ‘heterotroph’.Distinguish between heterotrophs and autotrophs in

terms of nutrient requirements for life.Summarise the process of photosynthesis in a word

equation and chemical equation. Identify structural features of photosynthetic

organisms that facilitate their ability to photosynthesise.

Active and Passive What do the terms mean? Watch the clip....

Is the whale shark an active feeder or a passive feeder?

Heterotrophs Actively obtain the energy they need for life

by feeding on organic matter found in their surroundings (food!)

They then use this organic matter to build and repair their cells.

Give some examples... What structural, physiological and behavioural

adaptations do heterotrophs have to help them obtain their food?

Autotrophs Organisms that just take up (absorb) the

energy they need from their surroundings. They build organic matter from simple

inorganic matter taken up from the air, soil or water.

Give some examples.....

So what about these guys...?

Carnivorous Plants Carnivorous plants still need water and

sunlight like other green plants to make food/energy (glucose) but they get their mineral nutrients from trapping and consuming animals.

Carnivorous plants are adapted to grow in places where the soil is thin or lacking nutrients, especially nitrogen, such as acidic bogs and rock outcroppings.

Photosynthesis Plants, algae and

some protists can make sugars by photosynthesis.

Sunlight energy is converted into chemical energy (in the form of glucose) in the chloroplasts found in the cytosol of cells.

What do you know already?

Plants use the energy from the sun to make molecules such as glucose, starch and proteins.

These molecules can then be used for food for the plant, but also for animals like us.

A waste product of the process is oxygen, which is released into the atmosphere.

The Importance The importance of photosynthesis is in the

conversion of unusable sunlight energy into usable chemical energy (glucose).

It is one of the most important biochemical processes, since nearly all life on Earth either directly or indirectly depends on it as a source of energy.

The EquationWord equation:

Balanced chemical symbol equation:

lightchlorophyll

lightchlorophyll

carbon dioxide+ water glucose+ oxygen

6CO2+ 6H2O C6H12O6+ 6O2

Or: six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen.

Plants absorb water through their roots, and carbon dioxide through their leaves.

Some glucose is used for respiration, while some is converted into insoluble starch for storage.

The stored starch can later be turned back into glucose and used in respiration.

Testing a green leaf for starch Will a plant that has been kept in a dark

cupboard for a few days contain starch in its leaves?

Structure of the Leaf Photosynthesis takes place mainly in the cells

of the leaves. Leaves are well adapted for photosynthesis –

its structure is well suited to its function. Leaves are made up of four main layers:

Upper epidermis Palisade layer Spongy layer Lower epidermis

Mesophyll layer

Inside the leaf

Structure of the Leaf

Waxy cuticle Vein/vascular bundle Air space Stoma Guard cell

Upper epidermis Lower epidermis Palisade cell Spongy mesophyll cell

Label the diagram with the structures:

Waxy cuticle

Upper epidermis

Palisade cell

Spongy mesophyll cell

Air spaceLower epidermis

Guard cellStoma

Vascular bundle (vein) – xylem and phloem

AB

C

D

E

F

GHI

Epidermis Single layer of cells on the upper and lower

surfaces of the leaf. Helps to keep the leaf’s shape. Has closely fitting cells:

Reduces evaporation from the leaf Prevents bacteria and fungi from getting in

Thin waxy layer covering epidermis called the cuticle – helps to reduce water loss further.

Have stomata. In woody stems, the epidermis is bark.

Stomata Singular: stoma Structures in the leaf epidermis. Consists of a pair of guard cells,

surrounding an opening called the stomatal pore.

The stomata can open and close by changes in the turgor and shape of the guard cells.

In some plants they are located on the lower epidermis only, others have stomata on both sides of the leaf.

Stoma

Guard cell

Leaf epidermal cell

How Do Stomata Work? Generally, they open during daylight hours

(whilst photosynthesis is taking place) and close during the night. Why? What do plants need to photosynthesise?

During the day they are open to allow carbon dioxide to diffuse into the leaf (and oxygen out) so photosynthesis can take place.

Mesophyll Tissue between the upper and lower

epidermis. Consists of two layers (see diagram).PALISADE CELLS: Function – to make food by photosynthesis. Hence, they have lots ofSPONGY MESOPHYLL CELLS Vary in shape, and fit loosely together. Many air spaces between them.

chloroplasts.

Air Spaces Whilst photosynthesis is taking place, the

air spaces in the mesophyll layer fill with carbon dioxide as it enters the leaf, and oxygen as it leaves the leaf.

Veins (vascular bundles) Xylem vessels carriy water needed for

photosynthesis to the mesophyll cells. The mesophyll cells take in water through

osmosis. Branching network – no cell is far away

from a water supply. Sugars made in mesophyll cells are passed

to the phloem cells – carry sugar away from the leaf to the stem.

The Ins and Outs of Photosynthesis There are two stages of photosynthesis:

1. A light dependent stage – needs water, light and chlorophyll. Gives off oxygen as a waste product.

2. A light independent stage – needs the products (hydrogen and energy) from the first stage, as well as carbon dioxide. Simple sugars are made.

Look at textbook pages 96-97 , and draw a simplified diagram to show the inputs and outputs of the two stages of photosynthesis.

When is photosynthesis most efficient? Chlorophyll absorbs red light best, followed by

blue. Green light is reflected, so not absorbed. Therefore photosynthesis is most efficient in red light, and least in green.

When these limiting factors are taken into account, photosynthesis can occur at the quickest rate: light intensity is high carbon dioxide concentration is high temperature is ‘warm’ – not too hot as enzymes

denature adequate water is provided.

LESSONS 3-4: Cellular Respiration and Digestion

LEARNING OUTCOMESBy the end of these lessons, you should be

able to:Understand and explain the inputs and

outputs of the significant stages in cellular respiration.

Understand the systems for processing nutrients in a range of different heterotrophic organisms.

ATP Adenosine triphosphate The form of energy used to maintain cellular

functions – like photosynthesis and respiration.

Made in the mitochondria where respiration takes place.

Respiration Respiration transfers chemical energy in the

form of glucose into ATP. Aerobic respiration uses oxygen. Anaerobic respiration occurs without the

presence of oxygen – less energy is released. In human muscles, lactic acid is produced.

The Equation

carbon dioxide+ waterglucose+ oxygen6CO2 + H2OC6H12O6 + 6O2

ADP + PiATP

Digestion The chemical process of breaking down large

organic molecules to a size that can be absorbed by the body.

Generally, four steps of digestion occur before a substance can become available for use by the cells of an animal: Ingestion Mechanical breakdown Chemical breakdown Absorption

The Four Steps1) Ingestion – intake of food into the mouth.2) 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.

3) Chemical breakdown – secretion or various digestive enzymes onto the food particles to further break down food particles into smaller and smaller particles.

4) Absorption – organic molecules pass through the lining of the intestinal walls into the blood stream to be distributed to cells.

Mechanical BreakdownJaws and teeth The jaws surround the

mouth and are opened and closed by muscles.

Movement of toothed jaws breaks food down into smaller pieces.

The structure of the teeth and jaws relates to the diet of the animal.

What are some examples?

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.

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

The Digestive SystemClass task – group work (2-3 people per topic)

presenting the different parts of a typical vertebrate digestive system:

The mouth and oesophagus The stomach The liver and gall bladder The pancreas The small intestine (duodenum) The small intestine (jujenum and ileum) Absorption in the small intestine The large intestine, rectum and anus

LESSON 5: Types of Digestive SystemLEARNING OUTCOMESBy the end of this lesson, you should be

able to:Understand and explain the systems for

processing nutrients in a range of different heterotrophic organisms.

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 in their gut.

Depending on where the bacteria live in the gut, herbivores are classified into two groups:

1) Foregut fermenters or2) Hindgut fermenters

Foregut Fermenters The foregut is comprised of the oesophagus and

the stomach. Ruminants (cattle, sheep, goats) have a vastly

enlarged, compartmentalised stomach for bacterial fermentation.

Draw a flowchart to show how digestion works in a ruminant animal.

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).

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

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.

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.

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

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