OCR Biology B2a-h

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B2a - Classification

There are two ways to classify organisms:

Artificial (based on observable characteristics)

Natural (based on similarities in DNA)

The seven levels of classification:

Kingdoms - Animals, Plants, Fungi, Bacteria, Proctoctists

Phyla/Phylum - Each Kingdom is sub-divided into Phyla. Animals = vertebrates (Arthropods, Cnidarians, Annelids, Molluscs)

Class/Classes - Each Phylum is divided into classes (e.g. Arthropods)

Orders - Each class is divided into orders (the class of mammals contains the orders 'Primates' and 'Carnivores'

Families - Orders are divided into families (the order of carnivores contains 'Felidae' and primates contains ' Homindae')

Genera - Families are divided into Genera (the family felidae contains the genus 'Panthera' and homindae contains 'Homo'

Species - Genera are divided into species, just one type of organism is included (the genus pathera contains 'Leo' and 'Tigns'

CNIDARIANS : SOFT-BODIED ORGANISMS MADE OF ONLY 2 LAYERS OF CELLS

MOLLUSCS : SOFT, UNSEGMENTED BODIES (SHELL)

ANNELIDS : RING-LIKE SEGMENTS

ARACHNIDS : 4 PAIRS OF JOINTED LEGS

INSECTS : 3 PAIRS OF JOINTED LEGS, 2 WINGS

MYRIAPODS : JOINTED LEGS ON EACH BODY SEGMENT

CRUSTACEANS : MORE THAN 4 PAIRS OF JOINTED LEGS

SPECIES = A group of similar organisms that are capable of inter-breeding to produce fertile offspring

Organisms are sometimes difficult to classify because:

Many organisms do not fit into one group

Hybrids

Asexual organisms (e.g. bacteria)

Evolution

Organisms that are not closely related yet look similar probably look the same because of:

Evolution

Common ancestors

Organisms that are closely related yet look very different probably look different because of:

Evolution

Different breeds

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B2b - Energy Flow

Food chains = show the transfer of energy from organism to organism

Sun - Grass (producer) - Grasshopper (Primary consumer) - Shrew (Secondary Consumer - Owl (Tertiary Consumer)

Plants = Photoautotroph - automatically creates own food in response to light (using sun's energy)

Pyramid of numbers = show the number of organisms at each trophic level

Pyramid of biomass = show biomass of total number of organisms at each trophic level. Always a true pyramid shape as energy is lost at each level

Efficiency of energy transfer = energy transferred to next level x100

energy in previous level

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B2c - Recycling

Carbon enters living organisms by photosynthesis

Carbon is released from living organisms by respiration and combustion

The key role of microbes in the carbon cycle is decomposing dead organisms and their waste

Humans are leading to an imbalance in the carbon cycle because of deforestation and combustion

The carbon cycle in a marine ecosystem:

Carbon dioxide dissolved in water

Photosynthesis leads to marine organisms producing carbon-compounds

Feeding and digestions leads to marine animals using carbon to produce calcium carbonate shells

Sedimentation leads to layers of shells at the bottom of the ocean forming sedimentary rocks (e.g. limestone)

Volcanic eruptions and weathering starts the process again

The nitrogen cycle:

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B2c - Recycling

Carbon enters living organisms by photosynthesis

Carbon is released from living organisms by respiration and combustion

The key role of microbes in the carbon cycle is decomposing dead organisms and their waste

Humans are leading to an imbalance in in the carbon cycle because of deforestation and combustion

The carbon cycle in a marine environment:

Carbon dioxide dissolved in water

Photosynthesis causes marine organisms to produce carbon compounds

Feeding and digestion leads to marine animals using carbon to produce calcium carbonate shells

Sedimentation leads to layers of shells at the bottom of the ocean forming sedimentary rock (e.g. limestone)

Volcanic eruptions and weathering starting the process again

The nitrogen cycle:

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B2d - Interdependence

Interdependence = the relationships between organisms that live together

Competition:

In habitats where organisms live together, there is often competition for resources such as:

Food

A mate

Nesting materials

Territory

Water

2 types of competition:

IntERspecific = competition between different species

IntRAspecific = competition within a species

Intraspecific is often more significant as members of the same species occupy the same ecological niche (way of life/role within ecosystem)

Parasitic relationships : In a parasitic relationship, the parasite benefits whereas the host is harmed.

Endoparasites = live inside the body e.g. tapeworm

Ectoparasites = live outside the body e.g. tick, flea

Mutualism = also called symbiosis; both species benefit.

e.g. legume and nitrogen-fixing bacteria

Benefits to legume:

Supplied with nitrate that can be combined with glucose to make amino acids, these join together to make proteins

Enables the plant to grow in soil lacking nitrate to reduce competition with other plants

Benefits to nitrogen-fixing bacteria:

Supplied with food in the form of glucose from the plant's photosynthesis

The nodules protects them from oxygen which would denature their enzymes

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B2e - Adaptations

Adaptations are characteristics that make an organism better able to compete and survive within an environment

Surface area to volume ratio:

SA : VOL (determined by size and shape)

If you increase the size of the animal the SA : VOL decreases

Organisms that have a large SA : VOL are either:

Small

Thin

or Flat

Organisms that have a small SA : VOL are either:

Large

Fat

or Round

COUNTER CURRENT HEAT EXCHANGE SYSTEM

(OPPOSITE) (THE FLOW OF BLOOD) (TRANSFER OF HEAT FROM ONE PLACE TO ANOTHER) (PHYSIOLOGICAL ADAPTATION)

Heat from the blood travelling through the artery is transferred into the colder blood flowing through the vein. This means that heat is retained close to the body's core, so enzymes are maintained at their optimum temperature.

Biochemical adaptations (e.g. thermostable enzymes)

Thermostable = thermo (heat) & stable (doesn't change)

Enzyme = protein (doesn't change when exposed to heat)

Denatured = active site has changed shape, reactions are not catalysed, reactions happen too slowly to maintain life e.g. respiration

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B2f - Natural Selection

Darwin's theory of natural selection:

Factors that may constitute 'struggle' for survival:

Harsh environment

Lack of food and water

Natural competition

Predators

Mates & Breeding

Lamarck's theory of natural selection:

A characteristic that is used more and more by an organism becomes bigger and stronger, and one that is not used eventually disappears

Any feature of an organism that is improved is passed onto its offspring

Speciation = the development of a new species from an existing one, it is usually the result of:

Geographical isolation

Reproductive isolation

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B2g - Population and pollution

Pollutant Effect Negative consequence(s)

Carbon dioxide and methane Global warming and greenhouse effect Ecosystem damaged

Sulphur dioxide Acid Rain Acidification of lakes

CFC's Depletion of the O-Zone layer Skin cancer & eye damage

Fertilisers Eutrophication Stagnant water system

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B2h - Sustainability

Endangered species = number of individuals of that species is very low and the species therefore is at risk of extinction

Sustainable development = development which meets the needs of the present without compromising the ability of future generations to meet their own needs

Fishing (increase mesh size, fishing quotas, limit of days at sea)

Woodland (Leaving stumps of trees, replanting)

Developed countries:

Produce more waste

Eat more food

Use more energy