Biological Diversity

GRADE 9 SCIENCE

BIOLOGICAL DIVERSITY

FINAL EXAM PREPARATION

Name: ______Homeroom: ______

STUDY GUIDE

SPECIES DIVERSITY (Textbook pages 10-23)

Variability

·  Diversity refers to differences, in this case differences in living things (biodiversity). The greater the diversity, the healthier the ecosystem.

·  A species is a group of organisms that have the same basic structure and can reproduce with one another. Organisms not of the same species cannot create fertile offspring.

·  Variability refers to the differences in structure and behavior that distinguish one living thing from another. Variability can exist between species (one species looks different from another) but can also exist within a species (a black bear may be black, brown, or even tan).

·  Sometimes these variations are subtle. For example, dogs, wolves and coyotes are each a distinct species yet they are very similar.

·  Probably the best known example of species variability is Darwin’s finches. Over years of having to adapt to a variety of environments and food sources on the Galapagos Islands, the bird’s beaks changed in order to allow them to successfully survive. This was through natural selection. Whereas all of the finches on the islands originally were seed eaters, they slowly adapted to other food sources such as leaves, insects, fruit and grubs. The structure of their beaks allows you to infer what their major food source would have been. The number of different dog breeds is another excellent example of variation within a species, although this has been through artificial selection rather than natural selection.

Niches

·  The niche of an organism describes its role. If, through natural selection, an organism can adapt to a niche that others have not, it will have a much better chance at survival. Also, if organisms can adapt to a broader environment (less specified) it increases their chance for survival. Examples of niches are shown below.

Organism / Where it lives / What it consumes / Affect on other organisms
Rabbit / Burrow / Water, grass / Feeds coyotes and hawks
Tree / Soil / Water, nutrients / Feeds consumers and gives 02

·  Birds in a park ecosystem may have the following niches – seagulls eat the left-overs, ducks have a bill and webbed feet so will stay near a park pond, robins will eat the worms, sparrows will eat seeds, woodpeckers will eat insects from the trees, etc. Adaptations to beaks, feet, flight and nesting behaviour allow the birds to fill different niches.

·  Resource partitioning (i.e. sharing the same niche for food and habitat) also allows more species to survive and thus increases the biological diversity of an ecosystem.

Several different species may share a tree by feeding or nesting at different levels.

·  If all organisms wanted the same food source, same habitat, same light, etc. there would be a great deal of interspecies competition and this would lead to less diversity.

Interdependencies

·  Food webs or food chains – producers (plants), consumers (animals) and decomposers.

·  Source of oxygen and food – animals need plants which produce oxygen and food (glucose) through photosynthesis and plants need animals for carbon dioxide and organic material for soil.

·  Interdependent organisms are symbiotic which means they depend on each other for one or more parts of their survival. Types of symbiosis include:

o  Commensalism (+/0) One benefits, other doesn’t notice. Birds nest in trees, fish live in poisonous corals, remora catch a ride on sharks

o  Mutualism (+/+) Both organisms benefit. Algae and fungus live together as lichen, flowers and pollinators, humans and domesticated animals

o  Parasitism (+/-) One benefits, the other is harmed. Tapeworms, mosquitoes...

o  Predation (+/-) Carnivore captures and feeds on prey.

o  Competition (-/-) when organisms complete, neither benefits. Hawks and coyotes compete for rabbits. The hawk is more successful and the coyote leaves, decreasing biodiversity and making the ecosystem less healthy.

The graph below shows a typical predation relationship. If the hare population decreases there will be fewer predators in the future. If the hare population increases, the predator population will begin to rise again.

Legend:

Flower

Butterfly

Years

Adaptation

·  Variation enables different species to survive in an ecosystem. In Darwin’s finches, those able to adapt survived because they developed beaks that allowed them to find new food sources. Darwin theorized that living things that could adapt new structures to meet their needs in a new environment would be the ones that would survive long enough to reproduce. This is the basis for Darwin’s theory of natural selection.

·  Natural selection in banded snails allows yellow snails to survive in sand while others would be picked off. Of the snails living in the ground, brown would have the best chance of survival. This adaptation was brought about by natural selection and increased the variability of this particular species, making it much more likely to survive, especially if one group was wiped out through a natural disaster or disease.

·  An ecosystem is an area where living organisms interact with non-living components. All of the different species together in the ecosystem make up the community. All of the members of one particular species makes up a population.

·  Variation plays a role in allowing species to survive under changing environmental conditions. For example, bacteria quickly develop a tolerance to antibiotics because those with immunity survive and reproduce, passing their immunity down to their offspring. In another example, Magpies are being killed off by West Nile Virus. If some Magpies are more immune, they will reproduce and their offspring will be immune, making the species stronger.

REPRODUCTION (Textbook pages 27-33, 43-45, 50-54)

Asexual Reproduction

·  Asexual reproduction involves only one parent so all offspring are identical - an exact duplicate of the parent. There are several types of asexual reproduction:

·  Binary fission – single celled organisms such as bacteria, amoebas, some algae.

Cell splits in two to make exact duplicate. This is the same process as mitosis

in multi-cellular organisms.

·  Budding – organisms such as hydra and yeast. Parent produces small bud which is a mini version of itself. It may stay on the organism or it may drop off and

become a new individual. THIS IS NOT A FLOWER BUD!

·  Spores (zoospores) – fungus, some algae, mould, ferns. Cell in one parent divides multiple times to produce an individual exactly like the parent. When conditions are right, the spores burst out and are usually carried by the wind or water to a place where they will be able to grow.

·  Vegetative reproduction – most plants are capable of vegetative reproduction where a part of plant can be cut or separated, and a new plant will develop from it without any outside fertilization source. Includes suckers (new tree from tree root), runners (above ground root grows away from plant) or bulbs (underground growth on root).

Sexual Reproduction in Animals

·  Sexual reproduction - must be a male and a female involved. Most plants and animals can reproduce sexually. Offspring have a mix of characteristics allowing an increase of variability within a species. Offspring will be different than either parent but will have traits inherited from both parents. There must be two specialized cells called gametes. Male gamete is the sperm, female gamete is the egg (ova). Sperm and egg each have half the normal number of chromosomes. When a sperm and egg combine, it is called fertilization and the resulting zygote has the full compliment of chromosomes for that species.

·  Sexual reproduction in animals includes the following steps:

Sperm penetrates egg (fertilization) forming the single-celled zygote.

The zygote cell begins to divide through cleavage.

Cells continue to divide and grow

Multicellular embryo develops.

Sexual Reproduction in Plants

·  The male structure is the stamen which consists of the anther and filament. The anther produces the pollen which is the male gamete. The filament holds up the anther so pollinators can reach it. The female structure is the pistil which consists of the stigma, style, ovary and ovules (female gametes). The stigma is sticky so pollen can stick to it. The style leads the growing pollen tube down toward the ovary. The ovary contains and protects the ovules and the ovules are the eggs waiting to be fertilized by the pollen.

·  Pollination occurs when pollen is transferred from the anther to the stigma. Flowers may pollinate themselves or pollen may be carried by butterflies, bees or wind from other flowers. This is called cross-pollination and it helps increase variability within the species of flower. Fertilization occurs when the pollen tube reaches the ovule. A zygote

is formed and divides to become an embryo. The embryo is protected inside of a seed.

·  Many plants can reproduce through both vegetative reproduction and pollination, but pollination is the preferred method since it leads to increases diversity of the species. Some animals, such as the hydra, can also reproduce sexually or asexually. Yeasts can also reproduce by both budding and sexual reproduction.

Discrete and Continuous Variation

·  Discrete variations do not have a range. The characteristic is defined as “either/or”.

·  Continuous variation characteristics can occur over a wide range.

Discrete Variation / Continuous Variation
Right OR left hand clasp / Mass – bone structure from small ð large
Straight OR Curved thumb / Height – short ðtall
Straight OR Pointed hairline (widow’s peak) / Length of arms, legs, hand - short ð long
Blood type – A or B or O or AB / IQ - from 0 ð 150+

Heritable Versus Non-Heritable Traits

·  Some characteristics are heritable (can be inherited from parents) and some are non-heritable (cannot be inherited from parents).

Examples of Heritable Characteristics / Examples of Non-Heritable Characteristics
Eye colour / Ability to play instruments
Skin colour / Scars
Height / Dyed hair colour
Bear hibernation / Seagulls hanging around dumpsters to feed

·  The environment can play an important role in certain characteristics (not things like eye colour or blood type since those are independent of environment). Even if you inherited average height and bone structure from parents, you will not attain these averages if you are severely malnourished as are many children in third-world countries. A plant that is kept in the dark will not have a chance to grow to its potential even if it inherited very strong traits from its parents. Weight (mass) is not an inherited trait but is very reliant on environment (you eat too much, you gain weight).

How Traits are Inherited

·  Traits are characteristics that are heritable – they can be passed down from generation to generation. Traits include things such as fur colour, eye colour, and skin colour.

·  Genes are responsible for inherited traits. A single gene controls a single trait.

·  Alleles are the “versions” of genes. If there was a jello gene, alleles would determine the flavour of the jello.

·  Some alleles for traits are dominant and some are recessive. Dominant traits show up far more often in the offspring than recessive traits because the presence of a dominant allele always masks the recessive one. Dominant alleles are represented by a capital letter (i.e. A) and recessive by lowercases (i.e. a).

·  Organisms that have inherited the same allele from both parents are called purebred or homozygous dominant (AA) or recessive (aa). If the offspring receives different kinds of alleles from each parent, they are said to be hybrid or heterozygous (Aa).

·  Incomplete dominance occurs when neither trait shows up – instead, the offspring has a combination of the parent traits. For example, if you cross a red sweet pea flower with a white sweet pea flower, the offspring may have pink flowers.

·  Offspring may not have characteristics of either parent. For example, two blue-eyed parents can have a brown-eyed child. Scientists now realize that some inherited characteristics are controlled by multiple genes so it is not always predictable.

The following examples show how you can use Punnett squares to determine inheritance patterns in offspring. Genotype refers to the genetic code (alleles) for the gene and phenotype refers to the appearance of the gene trait.

For these examples, we will use dog fur colour as the inherited trait.

The dominant fur colour is black and this allele will be represented by “F”.

The recessive fur colour is white and this allele will be represented by “f”.

The mother’s alleles will be along the top and the father’s alleles will be along the side.

Mother is homozygous dominant (two dominant alleles)

Father is heterozygous (one dominant, one recessive allele)

Offspring Genotypes:

50% of offspring are homozygous dominant

50% of offspring are heterozygous

Offspring Phenotypes:

All offspring are black.

GENETIC MATERIALS (Textbook pages 39-48, 67-71)

DNA

·  A large molecule called DNA (deoxyribonucleic acid), found in the nucleus of every cell, contains a complete set of instructions for making a new individual following the same basic blueprint as the parent. All life is related through the DNA molecule.

·  The arrangement of only four chemicals (A-C-T-G or base pairs) can be combined in billions of different ways to create all life. These chemical molecules make up the “steps” of the DNA ladder and they combine to form the genetic code. This code is similar for all living things but is unique for each individual.