Avariety of pear tree, known as bradford, was
originally introduced into the eastern united
states in the 1960s. today, this tree is crowding
out other plants in these states. this situation
best illustrates
(1) an unintentional negative effect of altering
an ecosystem
(2) how a foreign species is controlled in the
eastern united states
(3) that the introduction of a foreign species
does not affect food webs
(4) that serious environmental consequences
can be avoided by importing a foreign
species

80 points pls brainliest 1. what does a red shift mean? blue shift? 2. describe the big bang theory. according to this theory, how old is the universe? 3. scientists believe the universe is expanding. what is the evidence that supports this? 4. describe a nebula. 5. describe the 3 types of galaxies. what is a barred spiral galaxy? 6. what is a light year? how far is alpha centauri from earth? 7. describe the universal law of gravitation. be sure to include gravitational force between two objects. 8. describe the planets’ orbits around the sun. 9. what is the asteroid belt? where is it located? 10. describe rotation and revolution of earth. what determines an earth day and year? 11. how do galaxies exist? 12. compare and contrast the inner and outer planets. 13. what causes the seasons?