C7 bio end of unit test

unicellular organisms

A unicellular organism depends upon just one cell for all f its functions and is reliant on and vulnerable to their external environment

multicellular organisms

have cells, tissues and systems, specialised to perform different functions that collectively support the organism in maintaining homeostasis.

advantages of multicellularity

1. increased efficiency
2. longer life spans
3. dead cells have function
4. evolution and intelligence
5. bigger (usually better)
6. Relative (individual) cell size

increased efficiency

Cells become specialised to perform different and specific functions in a coordinated matter. Each cell has a different function and avoids duplication of work.

longer life spans

the death of a few cells does not kill a a multicellular organism. Increased number of cells\= larger lifespan. Specialised cells that protect and repair other cells, fight infections, heal wounds, regenerate tissues

dead cells also have function

the surface cells of many multicellular organisms are mainly dead and provide support, tools, and protection to the body. Eg. xylem in plants, human hair

Evolution and intelligence

being multicellular allows an organism to develop a higher level of understanding and adaptation to surroundings. Greater genetic diversity\= more adaptations and resistant to change as a species

bigger (usually better)

multicellular organisms can grow very large, larger brain\= increased intelligence, mobility\= can move and travel larger distances, reduces chance of being prey

relative (individual) cell size

Individual cells tend to be small, increasing the efficiency of an organism in terms of nutrient absorption and energy saving

Disadvantages in multicellularity

1. energy requirements and waste
2. takes longer to reach maturity and reproduce
3. infection is more likely
4. if one system fails, then potentially all can

energy requirements and waste

multicellular organisms require more energy to support multiple cells. Increased energy consumption also leads to an increased production of waste.

takes longer to reach maturity and reproduce

complex cellular makeup means that it takes longer for complex parts of the organism to reach maturity. More complex genetic makeup takes longer to mature.

Infection is more likely

infection becomes a risk from microbes (bacteria, protists, fungus), viruses and parasites that takes advantage of larger organisms.

Ingestion

food is taken through the mouth as large particles

Digestion

food broken down in the mouth, stomach and small intestine

Absorption

the products of digestion are absorbed across the gut wall

Egestion

unwanted material is eliminated by defecation

The alimentary canal

the human gut, around 9m long. Runs from mouth to anus, the tube which food passes through and is processed.

What are digestive accessory organs

aid in digestion but do not actually transfer food. Includes the salivary glands, pancreas, liver and gall bladder.

Main components of the digestive system

mouth, oesophagus, stomach, small intestine, large intestine

The mouth

Where food is physically broken down by the teeth and mixed with saliva from the salivary glands. Food is turned into bolus which makes this easier to swallow.

The oesophagus

muscular- contracts and relaxes to move food via peristalsis.

Epiglottis

a small flap which closes over the larynx when eating and drinking

The stomach

A muscular bag with a valve at either end. Churns food into chyme with oblique, longitudinal muscles. Contains gastric glands and has a coating of mucus to protect the stomach from HCl.

Two sphincters of the stomach

The cardiac sphincter at the top allows food in and prevents acid reflux. The plyoric sphincter at the bottom allows food to leave.

the liver

makes and secretes bile, which is alkaline and neutralises acidic chyme from the stomach to allow it to travel into the small intestine.

the gall bladder

stores bile which can be released into the small intestine when needed

the pancreas

secretes digestive enzymes

the small intestine

intestinal wall secretes enzymes. Small, soluble food molecules are absorbed through its walls.

Adaptations of the small intestine (structure for function)

- Large surface area (folded, more efficient absorption of nutrients)
- Thin wall (villi and capillary only one cell wide, shorter distance for nutrients to travel)
- Good blood supply (travels straight into bloodstream)
Additionally, there is microvilli on villi, protein channels and pumps, and mitochondria in epithelium

The large intestine

reabsorbs water and mineral ions such as Na+ and Cl-. The formation and temporary store of faeces. bacterial fermentation of indigestible materials (over 500 types of bacteria)

Methods of mechanical digestion

1. Chewing- mouth through mastication of teeth
2. Churning- food turned into chyme from contractions of the stomach.

Methods of chemical digestion

1. stomach acids- denatures proteins and other macromolecules
2. bile- contains bile salts which emulsify fats, increasing surface area for enzyme activity
3. enzymes- biological catalysts allowing reactions to occur at body temperature.

Three types of mammals

herbivores, carnivores, omnivores

Types of teeth (mammals)

incisors, canines, molars (and carnassials)

Teeth structure of herbivores

Incisors- small, chisel shaped for cutting plants
Canines- none
Molars- broad and flat with rough surfaces, grinding plants

Teeth structure of carnivores

Incisors- sharp/pointed for cutting small pieces of meat
Canines- large/sharp/pointed for gripping and killing prey
Molars- Narrow and cerated to cut meat into chunks and break bones

Teeth structure of omnivores

Incisors- wide, narrow and chisel shaped to cut
Canines- sharp and pointed for tearing
Molars- broad and flat to grind many foods

Diastema

large gap or spacing between the incisors and molars of a herbivore, providing room for the tongue to move food around to be chewed at different angles. Also stores plant matter to allow animals to eat more without stopping to swallow as frequently

Carnassials

Shearing teeth of carnivores used to slice and cut meat

Homodont teeth

all the same shape (dolphins)

Heterodont teeth

Different teeth (humans)

General trend of digestive systems in vertebrates

as complexity of digestive system increases, so does the availability of digestible food sources

Four types of vertebrate digestive systems

monogastric, avian, ruminants, pseudo-ruminants

monogastric digestive systems

a single chambered stomach found in carnivores.

Functions of the monogastric stomach

- digestion of raw meat is fast (compared to plants)
- if a scavenger, is short to avoid infection from bacteria (rotting meat)
- short, simple digestive tract
- No or small caecum as not consuming plants
(eg. dogs, raccoons)

avian digestive system

-no teeth but mouth with a beak
- crop (food storage)
- gizzard (breakdown of gravel like substances)
- two chambered stomach (proventriculus and true stomach)
- cloaca instead of anus
(eg. chickens and turkeys)

Ruminant digestive system

- foregut fermenters
- large, four chambered stomach
- symbiotic relationship with bacteria to digest cellulose
- most digestion occurs in the foregut (rumen)
- Large surface area
(eg. cows, sheep)

Pseudo-ruminant digestive system

- hindgut fermenters
- enlarged caecum to assist in breaking down cellulose
- 2-3 chambers with long digestive tract
(eg. horses, rabbits)

Gas exchange

the transfer of gases between an organism and the environment, required by all organisms. Occurs through diffusion.

Diffusion

the net movement of molecules from a region of high concentration to a region of low concentration, down the concentration gradient. A passive process.

Three factors impacting diffusion

- surface area
- concentration gradient
- distance that the substance is diffused
(also need moisture as oxygen and CO2 will only dissolve in an aqueous state)

Fick's Law of Diffusion

rate of diffusion\= (surface area * concentration gradient)/distance

Structures and mechanisms for gas exchange in fish

Gills
- filaments and lamellae, fine structures increase SA
- conc. of O2 is lower in water than air
- gills ventilated by swimming or gulping
- countercurrent exchange system (blood flows in opposite direction of water to maintain concentration gradient)

Structures and mechanisms for gas exchange in humans

Lungs
- alveoli walls are one cell thick
- produces mucus to maintain moisture
- O2 carried in red blood cells (oxyhaemoglobin)
- concentration gradient maintained by blood flow through capillaries and ventilation
- diaphragm contracts to allow breathing

Why do humans have a circulatory system?

multicellular systems are more complex and simple processes of diffusion become too slow, requiring transport systems.

Main functions of blood

- transport of oxygen and nutrients
- removal of carbon dioxide and waste
- movement of chemicals (hormones, chemical messengers)
- distribution of heat and maintaining body temp
- protection against disease
- maintain pH levels
- maintaining H20 content

What is blood composed of

plasma, red blood cells (erythrocytes), white blood cells (leukocytes), platelets (thrombocytes)

Plasma

straw-coloured fluid in which blood components are suspended. Transports CO2, glucose, amino acids, minerals, hormones, waste.

Structure of red blood cells

Biconcave discs that allows them to have an increased surface area for the transport of gases. Lack organelles (even a nucleus so cannot reproduce or repair). Contains haemoglobin and can change shape easily.

transport of gases in blood

Oxygen\= 3% plasma, 97% haemoglobin
Carbon dioxide\= 7-8% plasma, 22% carbaminohaemoglobin, rest as bicarbonate ions

The heart as a pump

a double pump with thin walled atria and thick walled ventricles, left side is more powerful.

Arteries

-carry blood away from the heart.
-very strong and contain elastic fibres to allow stretching under high pressure so it doesn't burst
-thin, muscular walls can contract to push blood along.

Veins

- carry blood towards the heart
- thin, non-muscular walls which rely on surrounding muscles to push blood along
- have valves to prevent blood from going in the wrong direction

Capillaries

- link arteries and veins
- only 1 cell thick, allows for the exchange of materials

Path of blood flow

1. superior and inferior vena cava (deoxygenated blood)
2. right atrium
3. right ventricle
4. pulmonary arteries
5. capillaries in lungs (oxygenates blood)
6. pulmonary veins
7. left atrium
8. left ventricle
9. aorta
10. arteries
11. capillaries (deoxygenates blood)
12. veins

Lumen

the inner wall of blood vessels which allow blood to flow within. Wide in veins.

Xylem

vascular tissue that carries water upward from the roots to every part of a plant. From ROOTS to LEAVES. Dead at maturity, only transports in one direction, provides structure for the plant.

Phloem

Living vascular tissue that carries sugar and organic substances throughout a plant. From LEAVES to REST OF PLANT. Cells are still living, paths are multidirectional.

Transpiration

Evaporation of water from the leaves of a plant. Phloem.

translocation

the transport of organic nutrients in the phloem of vascular plants. Xylem.

structure of the phloem

contains two cells\= sieve tubes and companion cells

sieve tubes

- end walls are perforated (sieve plates)
- elongated tubular shape
- strands of cytoplasm pass through each cell

Companion cells

- next to sieve tubes
- no nucleus and very little organelles to allow for maximal sugar flow

Evapotranspiration

the process of water removal through the stomata

What drives transpiration

heat from the sun

Flow of transport in vascular plants

1. roots (hairs increase SA)
2. water arrives at xylem
3. Water moves up the leaf through the xylem (into mesophyll through osmosis and used for cellular respiration)
4. Excess water removed through gas exchange in stomata
5. water evaporation creates negative pressure and draws more water through xylem
6. CO2 enters through stomata and used for photosynthesis
7. leaf is called the SOURCE of sugar
8. Sugar is loaded into phloem and transported from source to
SINKS, cells which use the sugar

difference in carnivore and herbivore digestive tracts

- carnivores have a very short digestive tract to avoid infection, small/no caecum.
- enlarged caecum for digesting cellulose, long digestive tract for absorption. Have a diastema instead of canines.

peristalsis

process of the throat/oesophagus moving food from mouth to stomach

Amylase

Enzyme in saliva that breaks the chemical bonds in starches. Also released in small intestine to replace ones that have been denatured in stomach.

Pepsin

An enzyme present in gastric juice that begins the hydrolysis of proteins. Start of protein breakdown in stomach. Only one that can function in an acidic environment in stomach.

Bile

alkaline, neutralises chyme from the stomach to allow for intestinal enzymes to break down.

Tripsin

Small intestine to break down proteins.

lacteal

fats don't get absorbed into blood vessels, only lacteals. Exist alongside a capillary, allows for the absorption of fats.

Homeostasis

the maintenance of variables/maintaining a relatively stable internal environment in the face of changing conditions

Why is homeostasis important

Biochemical reactions in cells can only occur when pH, salts, nutrients, and physical conditions (H20, temperature) are in certain limits for enzyme activity

Three components of homeostasis

receptor, control center, effector

Receptor

Senses a change in the environment and signals the control center

Control center

determines how to respond to the change and signals the effector

Effector

Receives the signal and adjusts accordingly

What does homeostasis control

concentration of respiratory gases in the blood, blood pH, blood glucose concentration (insulin and glucagon), thermoregulation, osmoregulation (ADH), concentration of essential ions, breathing and heart rate

What type of feedback loop is homeostasis?

Negative

Negative feedback loops

A response which is in the reverse of the change detected, functioning to reduce the change and return to equilibrium

Negative feedback loop process

1. A factor (stimulus) that affects the body's internal environment deviates from the optimum
2. This change is detected by the receptor or sensor
3. Message is relayed to the control center (brain)
4. Control center sends out nerve or hormone responses
5. Message received by effector
6. Effector brings out certain response which counterract the original deviation from the norm
7. System is returned to optimum

Positive feedback loops

A response that reinforces and amplifies the change detected. Will continue to amplify the initial change until the stimulus is removed.

Process of positive feedback loops

receptor detects change and an effector is activated to induce the same effect to promote further change eg. childbirth, ovulation, lactation, blood clotting

Body systems in charge of homeostasis

nervous system and endocrine system

Nervous system and homeostasis

central nervous system and peripheral nervous system nervous responses- sensory organs, receptors and effectors

Endocrine system and homeostasis

glands, chemical responses - hormones

Central nervous system

the brain and the spinal cord